Mammary tumorigenesis in chemical carcinogen-treated mice. VII. Prolactin and progesterone levels in BALB/c mice.

PIP: Pituitary and serum levels of prolactin (PRL) and serum levels of progesterone (P) were determined by polyacrylamide gel electrophoresis and radioimmunoassays in BALB/c female mice, 15-17 or 44 weeks old, treated with chemical carcinogens. Neither 1.5 mg 3-methylcholanthrene (MCA) nor 1.5-6 mg 7,12-dimethylbenz(a)anthracene (DMBA) markedly altered pituitary or serum levels of PRL in the younger mice, though DMBA increased the total pituitary content of PRL by about 33% in the 44-week-old mice. However, this increase was not correlated with the incidence of mammary tumors in the group or individuals. MCA increased serum P levels by about 22% within 50 days of the last treatment. This increase was attributable to higher serum levels of P during the diestrous and proestrous phases of the cycle. Adrenalectomy reduced serum P levels by about 60%, wheras ovariectomy had no effect. Serum P levels in 44-week-old rats were not affected by DMBA. The results fail to support the notion that MCA and DMBA promote murine mammary tumorigenesis by increasing pituitary and serum prolactin concentrations.^ieng

Potent inhibitory effect of a new antiestrogen (RU 16117) on the growth of 7,12-dimethylbenz[a]anthracene-induced rat mammary tumors.

At the daily dose of 24 mug for a period of 4 weeks, RU 16117 (11alpha-methoxyethinyl estradiol), a new antiestrogen, led to 65% reduction of the number of already established dimethylbenz[a]anthracene (DMBA)-induced mammary tumors in female Sprague-Dawley rats. Not only the tumor number but also the tumor size was reduced by RU 16117 in a manner similar to that seen after ovariectomy. The absence of an inhibitory effect of doses of 0.1 to 12.5 mug 17beta-estradiol (E2) per day, a dose-range which covers the low estrogenic activity of the RU 16117 doses used, suggested that the inhibitory effect of RU 16117 was not due to its estrogenic activity. Decreased levels of receptors for E2, progesterone, and prolactin were found in the tumors remaining after ovariectomy; treatment with the dose of RU 16117 sufficient to inhibit tumor growth (24 mug) had a similar inhibitory effect on the levels of E2 and prolactin receptors. These data suggested that a reduction of hormone receptor levels in the tumor tissue could be a mechanism by which RU 16117 acts as a potent inhibitor of the growth of DMBA-induced mammary carcinoma.

PIP: The new antiestrogen RU 16117, at doses of 8 or 24 mcg daily, had been shown to completely prevent the development of rat mammary cancer when given from the day after 7,12-dimethylbenz(a)anthracene (DMBA) administration. This study was undertaken to investigate the effect of this compound on the growth of DMBA-induced tumors which had already developed in Sprague-Dawley rats. The effect was compared with that of castration. Levels of receptors for 17beta-estradiol (E2), progesterone, and prolactin (PRL) were correlated with the response. At about 3 months after DMBA administration animals with palpable tumors were selected. The rats were then treated daily for 4 weeks with .1, .5, 2.5, or 12.5 mcg E2 or with 2, 8, or 24 mcg RU 16117 injected in .1 ml of 1% gelatin in .9% NaCl. Controls were injected with the vehicle alone. For comparison, a group of rats were ovariectomized. After 4 weeks' treatment rats were killed, blood collected, and a cytosol was prepared from tumor tissues. Binding assays and radioimmunoassays were done. 8 and 24 mcg doses of RU 16117 led to 45 and 65% inhibition of tumor number, respectively, and tumor size was markedly reduced. Lower doses had less effect. Ovariectomy had an effect similar to that of 24 mcg RU 16117. E2 doses did not change the number or size of tumors. Decreased levels of receptors for E2, progesterone, and PRL were found in the tumors remaining after ovariectomy. The 24 mcg dose of RU 16117 had a similar effect on levels of E2 and PRL receptors. It was considered likely that RU 16117 exerts its inhibitory activity at both the hypothalamic-pituitary and tumor levels.

Prolactin binding in ovariectomy-responsive and ovariectomy-nonresponsive rat mammary carcinoma.

Growth of the transplantable mammary tumor, MTW9, in W/Fu rats is greatly enhanced by elevated serum prolactin concentrations. This report compares the prolactin binding to tumor membranes in two mammary tumor strains derived from MTW9. Maximum binding to membranes of both tumors occurred at pH 7.6 after incubation for 30 hr at 4 degrees. The binding was inhibited only by polypeptide hormones that possess lactogenic activity. MTW9-P, an ovariectomy-responsive tumor developed in rats maintained on daily perphenazine injections, had 4-fold-higher prolactin binding than had MTW9MtT, an ovariectomy-nonresponsive tumor developed in rats bearing the mammosomatotropic pituitary tumor, MtTW10. Withdrawal of perphenazine from rats bearing MTW9-P caused a fall to normal of plasma prolactin, no tumor regression, and no significant change in prolactin binding. In contrast, resection of MtT resulted in tumor regression, a fall to normal of serum prolactin, and a nearly 3-fold increase in prolactin binding. Scatchard plots of prolactin binding data yield an apparent affinity constant, Ka, of 1.2 X 109 liters/mole for both tumors. The 4-fold-higher prolactin binding in the ovariectomy responsive variant suggests a positive correlation between ovariectomy response and the number of membrane prolactin-binding sites. No correlation between prolactin sensitivity and prolacting binding is apparent.

PIP: Prolactin binding in ovariectomy-responsive and ovariectomy-nonresponsive carcinoma in the Wistar/Furth rat is compared. The time course of binding of prolactin at 4, 24, ad 37 degrees for mammary tumor (MTW9) coimplanted with MtTW10, a mammosomatotropic pituitary tumor (MTW9-MtT) or with MTW9 maintained with daily perphenazine injections (MTW9-P) was measured. Maximum binding to membranes of both tumors occurred at 4 degrees after about 30 hours incubation. The binding was inhibited by polypeptide hormones that possess lactogenic activity. Mammary tumors from animals maintained on perphenazine had a 4-fold greater binding capacity than did tumors from MtT-supported animals. When perphenazine therapy was halted the binding capacity of MTW9-P membranes was unaffected. This result held when MTW9-P animals were ovariectomized. Resection of MtT resulted in tumor regression, a fall to normal of serum prolactin, and a nearly 3-fold increase in prolactin binding. Scatchard plots of prolactin binding data yield an apparent affinity constant, K(a) of 1.2 X 10(9) liters/mole for both tumors.

Prolactin binding to mammary gland, 7,12-dimethylbenz(a)-anthracene-induced mammary tumors, and liver in rats.

Specific binding of radioactively labeled prolactin was determined in membrane preparations from mammary glands and livers of rats during pregnancy and lactation. Prolactin binding to mammary gland increased throughout late pregnancy and early lactation, reached a maximum on Day 11 of lactation, and then declined. Maximum prolactin binding to liver membrane preparations was observed during late pregnancy and declined throughout lactation. Estradiol benzoate (20 mug/day), administered on Days 5 to 10 of lactation, reduced prolactin binding to mammary gland by 55%, increased binding to liver 2-fold, and reduced litter weight gain by 25%. Prolactin binding to 7,12-dimethylbenz(a)anthracene-induced mammary tumors was 3 times higher than that observed in lactating mammary gland. Administration of prolactin enhanced tumor growth but decreased specific prolactin binding to tumors. Lergotrile mesylate inhibited and estradiol benzoate (2 mug/day) enhanced tumor growth, but neither treatment affected prolactin binding to tumor membrane preparations. In contrast, higher doses of estradiol benzoate (20 mug/day) inhibited tumor growth and reduced prolactin binding. Prolactin binding varied widely within all groups of mammary tumors and was not clearly related to growth response or to altered circulating estrogen and/or prolactin levels. Hormone dependence in this animal tumor model is complex and may not be predicted on the basis of prolactin-binding capacity alone.

PIP: Experiments designed to study the changes in prolactin (PRL) binding to rat mammary tissue and liver during pregnancy and lactation, to study the relationship between PRL binding and growth in 7,12-dimethylbenz(a)anthracene (DMBA)-induced mammary tumors and to measure PRL binding in DMBA tumors, lactating mammary gland and liver following administration of pharmacological doses of estrogen are described. Specific binding of radioactive PRL binding to mammary gland increased throughout late pregnancy and early lactation, reached a maximum on Day 11 of lactation and then declined. Maximum binding to liver membrane preparations was observed during late pregnancy and declined throughout lactation. The administration of 20 mcg estradiol benzoate (EB/day on Days 5-10 of lactation, reduced PRL binding to mammary gland by 55%, increased binding to liver 2-fold and reduced litter weight gain by 25%. PRL binding to DMBA-induced mammary tumor was 3 times higher than that observed in lactating mammary gland. PRL administration enhanced tumor growth but decresed specific PRL binding to tumors. Lergotrile mesylate inhibited and 2 mcg EB enhanced tumor growth, but neither treatment affected PRL binding to tumor membrane preparations. However, 20 mcg EB inhibited tumor growth and reduced PRL binding. PRL binding varied widely within all groups of mammary tumors and was not clearly related to growth response or to altered circulating estrogen and/or PRL levels. It is concluded that hormone dependence in the rat tumor model is complex and may not be predicted on the basis of PRL-binding capacity alone.

Effects of 17 beta-estradiol and medroxyprogesterone acetate upon MtTW15 mammosomatotropic pituitary tumor growth and hormone production in male and female rats.

The purpose of this study was to characterize the effects of two functionally diverse steroids, 17 beta-estradiol and medroxyprogesterone acetate (MPA), on MtTW15 rat mammosomatotropic pituitary tumor growth and hormone production. Steroid responsiveness, as well as the hormonally autonomous nature of the tumor, was studied by treating both male and female tumor-bearing rats for 7 weeks with weekly injections of either 17 beta-estradiol (600 ng/g body weight/week) or MPA (200 microgram/g body weight/week) and, subsequently, comparing both the tumor weights and the in vivo production of growth hormone (GH) and prolactin (PRL) among the treatment groups. Large tumors (6 to 20 gm) were obtained in all treatment groups, indicating hormonal autonomy; however, tumors were markedly smaller, on the average, in untreated males an ovariectomized females. Treatment of such rats with 17 beta-estradiol stimulated tumor growth. Radioimmunoassay of tumor and serum GH and PRL levels in all treatment groups indicated the following: (a) tumors from untreated male or female hosts did not favor the production of one hormone over the other to any great extent; (b) MPA, however, promoted significant increases (p less than 0.05) in GH production in both male and female tumor-bearing rats while having little effect on the production of PRL; and (c) 17 beta-estradiol significantly inhibited (p less than 0.05) GH production and promoted PRL production by tumors borne by either sex. Selected studies utilizing multiple doses of MPA (1 to 500 microgram per gm body weight per week) and 17 beta-estradiol (10 to 800 ng per gm body weight per week) were accomplished and demonstrated that hormone production can be influenced in a dose-related manner. These results indicated that the estrogen-induced MtTW15 rat pituitary tumor is hormonally autonomous, yet divergently responsive to two different classes of steroidal compounds, thus making this tumor line an appropriate model for the study of hormonally responsive pituitary tumor cells.

PIP: The purpose of this study was to characterize the effects of 2 functionally diverse steriods, 17beta-estradiol and (MPA) medroxyprogesterone acetate on MtTW15 rat mammosomatotropic pituitary tumor growth and hormone production. Steroid responsiveness, as well as the hormonally autonomous nature of the tumor, was studied by treating both male and female tumor-bearing rats for 7 weeks with weekly injections of either 17beta-estradiol (600 ng/g body weight/week) or MPA (200 mcg/g body weight/week) and, subsequently, comparing both the tumor weights and the in vivo production of (GH) growth hormone and (PRL) prolactin among the treatment groups. Large tumors (6 to 20 gm) were obtained in all treatment groups, indicating hormonal autonomy; however, tumors were markedly smaller, on the average, in untreated males and ovariectomized females. Treatment of such rats with 17beta-estradiol stimulated tumor growth. Radioimmunoassay of tumor and serum GH and PRL levels in all treatment groups indicated the following: (a) tumors from untreated male or female hosts did not favor the production of 1 hormone over the other to any great extent; (b) MPA, however, promoted significant increases (p 0.05) in GH production in both male and female tumor-bearing rats while having little effect on the production of PRL; and (c) 17-estradiol significantly inhibited (p 0.05) GH production and promoted PRL production by tumors borne by either sex. Selected studies utilizing multiple doses of MPA (1 to 500 mcg/gm body weight/week) and 17 beta-estradiol (10 to 800 ng/gm body weight/week) were accomplished and demonstrated that hormone production can be influenced in a dose-related manner. There results indicated that the estrogen-induced MtTW15 rat pituitary tumor is hormonally autonomous, yet divergently responsive to 2 different classes of steroidal compounds, thus making this tumor line an appropriate model for the study of hormonally responsive pituitary tumor cells.

Prolactin binding to R3230AC mammary carcinoma and liver in hormone-treated and diabetic rats.

Specific 125I-labeled prolactin binding was measured in membrane particles prepared from R3230AC mammary carcinoma and liver of tumor-bearing Fischer rats after either prolactin, estrogen, or lergotrile mesylate treatment, or after the induction of diabetes by streptozotocin. Hormone binding to tumors was decreased by treatment with prolactin (0.5 or 1 mg/day) or estradiol valerate (7.5 mg/kg/week). In contrast, prolactin treatment did not affect prolactin binding to liver membrane particles, but estradiol valerate treatment resulted in a four-fold increase in prolactin binding to this tissue. Lergotrile mesylate, which lowers plasma prolactin levels, did not affect tumor growth or prolactin binding to either tumor or liver. Prolactin binding to both tumor and liver was significantly reduced in diabetic rats, suggesting that insulin may play an important role in controlling tissue sensitivity to prolactin. Specific binding of 125I-labeled prolactin to enzymatically dissociated cells from R3230AC tumors was demonstrated in vitro. The binding capacity of the cells was found to be of the same order of magnitude as the binding capacity in membrane preparations when appropriate corrections were applied for yields of cells and membranes. R3230AC tumor, which is responsive to prolactin appears therefore to be a useful model system for further study aimed at elucidation of growth and metabolic response to the hormone prolactin in breast cancer.

PIP: Specific iodine-125-labeled prolactin binding was measured in membrane particles prepared from R3230AC mammary carcinoma and liver of tumor-bearing Fischer rats after either prolactin, estrogen, or lergotrile mesylate treatment, or after the induction of diabetes by streptozotocin. Hormone binding to tumors was decreased by treatment with prolactin (.5 or 1 mg/day) or estradiol valerate (7.5 mg/kg/week). In contrast, prolactin treatment was without affect on prolactin binding to liver membrane particles, but estradiol valerate treatment resulted in a 4-fold increase in prolactin binding to this tissue. Lergotrile mesylate, which lowers plasma prolactin levels, had no affect on tumor growth or prolactin binding to either tumor or liver. Prolactin binding to both tumor and liver was significantly reduced in diabetic rats, suggesting that insulin may play an important role in controlling tissue sensitivity to prolactin. Specific binding of iodine-labeled prolactin to enzymatically dissociated cells from R3230AC tumors was demonstrated in vitro. The binding capacity of the cells was found to be of the same order of magnitude as the binding capacity in membrane preparations when appropriate corrections were applied for yields of cells and membranes. R3230AC tumor, which is responsive to prolactin, appears therefore to be a useful model system for further study aimed at elucidation of growth and metabolic response to the hormone prolactin in breast cancer.

Grwoth hormone, prolactin, and cortisol in dogs developing mammary nodules and an acromegaly-like appearance during treatment with medroxyprogesterone acetate.

PIP: Concentrations of (GH) growth hormone, (PRI) prolactin, cortisol, progesterone, and (MPA) medroxyprogesterone acetate were determined by RIA in blood sera collected from beagle bitches 17 months after initiating treatment with MPA (75 mg/kg.3 months; n = 12) MPA vehicle (controls; n = 12), or progesterone implants which produced physiological levels of progesterone (13.8 + or - 2.1 ng/ml; n = 12). In the MPA-treated bitches, mean MPA levels were 104 + or - 6 ng/ml, mean GH levels were elevated (9.5 + or - 3.0 vs. 0.4 + or - 0.1 ng/ml; P 0.01); mean PRL levels were unchanged (13.7 + or - 2.8 vs. 12.6 + or - 1.2 ng/ml); and mean cortisol levels were suppressed (1.7 + or - 0.2 vs. 13.7 + or - 1.4 ng/ml; P 0.01) in comparison to those in control animals. None of these parameters was significantly affected by progesterone treatment. External signs of an acromegaly-like condition and large mammary gland nodules (diameters, 5 mm) were noted in, and limited to, 9 bitches with elevated ( 2.5 ng/ml) GH levels (12.8 + or - 3.0 ng/ml). These were 8 MPA-treated bitches which developed the acromegal-like condition during treatment and 1 progesterone-treated bitch which appeared acromegalic before treatment and in which the condition was considered to have developed spontaneously. The data suggest that the acromegaly-like changes and large mammary nodules in dogs administered the contraceptive progestin MPA occurred as a result of MPA-induced elevations in GH. The results do not preclude the possibility that the MPA-induced suppression of cortisol and/or the direct action of MPA on the mammary glands also contributed to mammary nodule formation. MPA-treated dogs may also provide a unique experimental model for studying chronic elevations in endogenous GH levels and for testing compounds for their ability to suppress GH levels.^ieng

The nocturnal rise of human prolactin is dependent on sleep.

PIP: Further evidence that there is a relationship between prolactin rise and sleep is offered by this study that delayed sleep onset and inverted the normal sleep-waking cycle in 4 normal patients (3 women and 1 man). The inversion schedule lasted 3 weeks, and at its conclusion a final 12-hour laboratory study was carried out measuring the plasma levels of human prolactin and growth hormone by radioimmunoassay. In the first female subject, mean prolactin levels (ng/ml) were, for baseline and after shift, 7 and 8.3; for case 2 (female) the values were 7.3 and 5.9; for case 3 (male) the levels were 6.1 and 6.1; and for the last case, the levels were 4.7 and 4.3, respectively. Values for growth hormone were (ng/ml) 1.5 and 1.5 for Case 1 for baseline and after shift, respectively; 1.1 and 2.5 for Case 2, respectively; 1.8 and 1.1 for Case 3, respectively; and 7.3 and 5.2 for Case 4, respectively. Prolactin release shifted immediately and completely with shifts of sleep onset of 3, 6, and 12 hours. Thus, it is concluded that the nocturnal rise is dependent on the occurrence of sleep, not on the inherent rhythm related to time of day.^ieng

Changes in the prolactin response to thyrotropin-releasing hormone (TRH) during the menstrual cycle of normal women.

Serum prolactin (PRL) and thyrotropin (TSH) levels were measured after iv administration of 200 microng of synthetic thyrotropin-releasing hormone (TRH) in 20 normal women ages 18 to 34. Ten women received TRH on days 7 to 8 of the menstrual cycle and 10 women received TRH on days 21-22. Although there was no difference in the dose of TRH relative to body weight in the two groups of women, the peak PRL level after TRH stimulation was greater in the women studied on day 21-22 (48.5+/-5.7 ng/ml, mean+/-SE) than on day 7-8 (35.2+/-4.2 ng/ml) of the cycle (P less than 0.05). In contrast, TSH rose to a greater degree in the preovulatory phase (13.8+/-1.8 micronU/ml) than the luteal phase (7.7+/-0.7 micronU/ml of the cycle (P less than .01). Studies of the PRL and TSH response after TRH administration should take the phase of the menstrual cycle into account.

PIP: The effects of synthetic thyrotropin-releasing hormone (TRH), administered iv in a dose of 200 mcg, on serum prolactin and thyrotropin levels were measured in 20 women aged 18-34 years. 10 subjects received TRH on Days 7-8 of the menstrual cycle, and the remaining 10 were treated on Days 21-22. The dose/body weight ratio was similar in both groups. The peak prolactin level following TRH administration was 48.5 + or -5.7 ng/ml in women treated on Days 21-22 and 35.2 + or -4.2 ng/ml in those treated on Days 7-8 (p less than .05). Conversely, serum levels of thyrotropin were significantly (p less than .01) higher in the preovulatory phase than the luteal phase (13.8 + or -mcU/ml and 7.7 + or -.7 mcU/ml, respectively). It is recommended that the interpretation of the prolactin response to TRH should take the phase of the menstrual cycle into account.

The relationship between suckling-induced prolactin response and lactogenesis.

The PRL response to suckling was studied during the first week of the puerperium. Mean basal levels of PRL showed no significant changing during the first week of the puerperium, but there were progressive rises in both the maximum suckling-induced response and the total area under the response curve, which reached peak values on the fourth day after delivery. Despite large variations between individuals in basal PRL levels (range, 0.3-7.0 U/liter), peak suckling-induced response (range, 0.1-9.9 U/liter), and total response (range, 0.6-63.0 arbitrary units), there was much less variability within individuals between consecutive feeds. Using an electronic balance, 20 patients on days 5 and 6 were classified either as good feeders (greater than 60 g milk/feed) or poor feeders (less than or equal to 60 g milk/feed) on the basis of 2 consecutive test weights. The mean PRL response to suckling in 11 good feeders was no different from that in 9 poor feeders, and there was no significant correlation between milk yield and PRL response. Six patients whose infants were in the special care nursery had lactation initiated and maintained by breast pump for an average of 5.6 days. Although the PRL response to the breast pump was very small, these patients also had satisfactory milk yields (mean, 86 g). Although the presence of PRL is essential for lactation, the data in this paper suggest that there is no close temporal correlation between PRL concentrations and milk yield.

A separate mechanism of gonadotropin recovery after pregnancy termination.

To further elucidate the mechanism of return of pituitary secretory function after gestation, eight women were studied for up to 55 days after pregnancy termination. As long as serum estradiol (E2) and progesterone (P) levels were elevated, serum FSH remained low. Four to 6 days after abortion, serum E2 and P decreased to levels seen in the early follicular phase, and thereafter the initial increase in FSH occurred while serum beta-LH remained undetectable. After the initiation of FSH secretion, the levels fluctuated within the normal follicular phase range, resulting in a steady increase of E2 to a mean preovulatory peak of 257 +/- 37 pg/ml at a mean time of 21 +/- 1.3 days after pregnancy termination. This E2 peak was followed by FSH and LH peaks and subsequent ovulation. In contrast to FSH, serum beta-LH levels increased only after PRL-concentrations diminished to 30 ng/ml or less. This initiation of beta-LH secretion followed the advent of FSH secretion in six of eight patients. Therefore, a temporally separate mechanism of FSH and LH secretion after pregnancy termination is theorized. The theory of FSH occurs soon after the E2 and P levels decline while PRL levels are still elevated. However, the secretion of beta-LH increases only after levels have risen from the postabortion decline.

Acute and chronic estrogen effects upon serum somatomedin activity, growth hormone, and prolactin in man.

Estrogen (E) reduces bioassayable GH-dependent serum somatomedin (SM) activity in acromegalics without affecting plasma growth hormone (GH) levels and inhibits the rise of SM activity normally produced by GH administration in GH-deficient subjects. We have now investigated the effect of E administration on serum SM activity and on plasma GH and prolactin (PRL) in 6 adult male subjects without pituitary pathology. Chronic E administration (ethinyl estradiol 0.5 mg/day for 7 to 70 days) reduced serum SM activity by 40 to 62% in each of 4 subjects (P less than 0.02 to less than 0.001). In 3 of the subjects, basal GH levels increased by 75 to 300% (P less than 0.05 to less than 0.001) and basal PRL levels increased by 90 to 200% (P less than 0.01 to less than 0.001). While iv administration of normal saline did not significantly affect either SM or GH, iv administration of E (bolus injection of 25 mg conjugated estrogens, USP) to 5 subjects resulted in: a) a 46 to 80% decrease in serum SM activity in all subjects, proceeding with an apparent half-life of 2 hours, becoming significant (P less than 0.05) at 2 hours (1 subject) to 3 hours (4 subjects), maximal at 6 hours, and persisting for 12 to 24 hours; b) GH elevation to 3 to 16 times baseline level (P less than 0.01) at 2 to 3 hours in 4 subjects; and c) no significant change of PRL levels in any subject. The mean GH response to iv E was maximal at a time (2 hours) when the mean SM activity had decreased only 20% and subsided well before the nadir of SM activity. The one patient without GH response to chronic or acute E administration may have been affected by absorption of triamcinolone being applied topically during the study. These results demonstrate that in males with normal pituitary function, E reduces serum SM activity, enhances basal GH and PRL secretion, and, upon iv injection, stimulates acute GH release. Although opposite chronic E effects upon GH and SM activity support a putative negative SM-GH feed-back mechanism, iv E administration apparently provokes acute GH release by a different mechanism. The half-life of serum SM activity in the human is probably much shorter than previously estimated.

PIP: Acute and chronic estrogen effects upon serum somatomedin (SM) activity, growth hormone (GH), and prolactin were studied in adult male subjects. Administration of .5 mg ethinyl estradiol/day for 7-70 days reduced serum SM activity by 40-62% in each of 4 subjects (p less than .02 to less than .001). In 3 subjects, basal GH levels increased 75-300% (P less than .05 to less than .001) and basal prolactin levels increased by 90-200% (p less than .01 to less than .001). Intravenous (iv) administration of saline did not markedly affect SM or GH while the iv administration of 25 mg conjegated estrogens to 5 subjects resulted in: 1) a 46-80% decrease in serum SM activity in all subjects proceeding with an apparent 1/2-life of 2 hours, becoming significant (p .05) at 2-3 hours and persisting for 12-24 hours, 2) GH elevation to 3-16 times baseline level (p .01) at 2-3 hours and 3) no marked change in prolactin levels. These results indicate that in males with normal pituitary function, estradiol reduces serum SM activity, enhances basal GH and prolactin secretion and, upon iv injection, stimulates acute GH release. It is suggested that the 1/2-life of serum SM activity in the human is probably much shorter than previously estimated.

The relationship of changes in serum estradiol and progesterone during the menstrual cycle to the thyrotropin and prolactin responses to thyrotropin-releasing hormone.

The responses of serum TSH and PRL to TRH (500 microgram) were studied in normal young women in the early follicular, periovulatory, and midluteal phases of the menstrual cycle in order to examine the relationship of these responses to the levels of estradiol relationship of these responses to the levels of estradiol (E2) and progesterone. Each woman was studied twice in each phase in order to assess intraindividual variability. There was no significant difference in either the TSH or PRL responses among the phases of the menstrual cycle nor was either response affected by the periovulatory rise in E2 or by the luteal rise in both E2 and progesterone. Thus, the interpretation of the TSH and PRL responses to TRH in normal women is not affected by the menstrual cycle although both responses are greater in women that in men. Both the peak TSH and peak PRL after TRH were highly correlated with the basal levels of TSH (r = 0.85; P less than 0.01) and PRL (r = 0.67; P less than 0.01), respectively, indicating that the TSH and PRL responses to TRH in women are directly proportionate to the basal levels of the respective hormones, as previously shown for the TSH response in men. The mean intraindividual variability (coefficient of variation) of the TSH response to TRH was 18%, but ranged as high as 56%, while that of the PRL response was 16% and ranged up to 31%; variability was not affected by the phase of the menstrual cycle. The normal range of the peak TSH after TRH in women is 7-33 microU/ml (mean +/- 2 SD); however, because of the variability, a normal woman may sometimes have a peak TSH after TRH as low as 4 microU/ml. Repeating the test will result in a normal value if the woman is truly normal. Similarly, the normal peak PRL after TRH in women is 22-111 ng/ml (mean +/- 2 SD); usually, however, the lower limit is 30 ng/ml with lower values due to intraindividual variation. The data suggest that the higher average level of E2 in women compared to women, but that the cyclic changes in serum E2 or progesterone in women have little or no additional effect.

PIP: The relationship of changes in serum estradiol and progesterone during the menstrual cycle to the thyrotropin (TSH) and prolactin (PRL) responses to thyrotropin-releasing hormone (TRH) was investigated. Serum TSH and PRL responses to TRH (500 mcg) were studied in 10 healthy women, aged 19-32 years, in the early follicular, periovulatory, and midluteal phases of the menstrual cycle. Peak TSH and peak PRL after TRH were highly correlated with the basal levels of TSH (R=.85; P .01) and PRL (R=.67; P .01); respectively, indicating that the TSH and PRL responses to TRH are directly proportionate to the basal levels of the respective hormones. Neither TSH and PRL responses to TRH nor variability was affected by the phase of the menstrual cycle. The normal range of peak TSH after TRH was 7-33 mcU/ml and the normal range of peak PRL after TRH was 22-111 ng/ml. These results suggest that the higher average level of estradiol in women compared to men may account for the greater responses in women, however, the cyclic changes in serum estradiol or progesterone in women have little or no additional effect.

Pituitary autonomy in hyperprolactinemic secondary amenorrhea: results of hypothalamic-pituitary testing.

Twenty-seven women with secondary amenorrhea of greater than six months duration were subjected to multiple testing of hypothalamo-pituitary function. They were divided into normo-prolactinemic (Group 1 mean serum prolactin (PRL) 9.8 ng/ml; range 6.8 to 13.0 ng/ml; n=9) and hyperprolactinemic (Group 2 mean 37.5 ng/ml; range 19.2 to 93.7 ng/ml; n=18) groups on the basis of 4 weekly baseline determinations. Group 2 had significantly (P less than .05) lower serum LH and urinary pregnanediol levels than did Group 1; there was no statistical difference between the groups in serum FSH, T4, T3 or urinary estrogen measurements. Two women in Group 2 were found to have a pituitary chromophobe adenoma. Group 2 women showed no significant rises in serum PRL following stimulation tests with thyrotropin releasing hormone (TRH, 200 microng iv) and metoclopramide (10 mg orally), which caused significant responses in Group 1. The TSH response to TRH was, however, preserved in Group 2, while it was subnormal in Group 1 subjects. Both groups showed similar FSH and LH responses to luteinizing hormone-releasing hormone (LHRH, 25 microng iv). No significant suppression of serum PRL was seen in Group 2 patients given L-Dopa (500 mg orally),, which produced a significant response (P less than 0.05) in Group 1 subjects, while all patient showed marked reduction in serum PRL values following 2-bromo-alpha-ergocryptine (CB-154, 2.5 mg orally). When compared with other Group 2 members, the 2 cases with proven pituitary adenomata gave similar responses to the stimulation-inhibition tests and were not clearly distinguished on this basis. We conclude: 1. The pattern of PRL responses to dynamic tests, although of pathophysiological interest an autonomous pituitary lesions in patients with hyperprolactinemic secondary amenorrhea. 2. Such dynamic tests, although a pathophysiological interest, provide no clinical information additional to that provided by the mean basal serum PRL value. 3. In clinical practice, such dynamic tests should be confined to patients with mean serum PRL levels at around the upper limit of the normal range.

Hormonal evaluation of the intrauterine progesterone contraceptive system.

Nine women were studied for one menstrual cycle prior to the insertion of an intrauterine progesterone contraceptive system (IPCS) delivering 65 microng progesterone/day into the uterus and again at 1 month after its insertion. Eight of these women were again studied between 6-8 months after the insertion of the IPCS. Luteinizing hormone (LH), follicle-stimulating hormone (FSH), estradiol-17beta, progesterone, prolactin and relaxin were measured in each plasma sample. The data from each study were combined according to the day of the LH peak. Ovulation occurred in all the cycles studied in spite of an elevation in plasma estradiol-17beta and a depression of prolactin and relaxin immunoactivities at the 6-8 month follow up. Menstruations noted at the 6-8 month of use occurred while levels of estradiol-17beta and progesterone were elevated.

PIP: Plasma levels of luteinizing hormone, follicle stimulating hormone, estradiol-17beta, progesterone, prolactin, and relaxin were studied in 9 women before and after insertion of an Alza, progesterone-releasing, IUD. The IUD releases approximately 65 mcg/day of progesterone into the uterus. The lengths of the preovulatory and postovulatory phases of the menstrual cycle were not affected by the device. Ovulation occurred in all the cycles, even though plasma levels of estradiol-17beta were significantly (p less than .05) increased and plasma levels of prolactin and relaxin were significantly (p less than .05) decreased as late as 6-8 months after insertion. During menstruation at 6-8 months after insertion, plasma levels of estradiol-17beta and progesterone were high. The results are discussed.

Prolonged elevation of hypothalamic opioid peptide activity in women taking oral contraceptives.

To examine the hypothesis that endogenous opioid peptide activity is chronically elevated by oral contraceptives, we infused either naloxone or saline into 10 women during the use of, or 5-6 and 9-10 days after stopping, combination birth control pills. A paradoxical increase in prolactin occurred with naloxone infusion during and 5-6 days after stopping the pills. Serum LH levels were not significantly elevated by naloxone until 9-10 days after cessation of pill use. These results suggest that hypothalamic opioid peptide activity is continuously elevated in women taking oral contraceptives.

Biphasic change in pituitary capacity induced by estrogen in hypogonadal women.

PIP: 5 healthy postmenopausal women aged 52-59 years with elevated gonadotropin levels and low estradiol (E2) (10+ or -1.5 pg/mol) concentrations volunteered for this study which measured changes in responses to pulses of luteinizing hormone-releasing factor (LHF) (10 mcg at 2-hour intervals 3 times) and thyroid-releasing factor (TRF) (200 mcg at 2-hour intervals 3 times) for luteinizing hormone (LH), follicle stimulating hormone (FSH), and prolactin (PL) before and during administration of a large dose of ethinyl estradiol (EE) (400 mcg/day) for 5 days. Responses to LRF and TRF stimulation on the 2nd and 5th days of EE treatment were studied in 2 experimental periods in the same individual at an interval of at least 10 weeks between treatments. During 5 days of EE treatment, LH 1st declined (50%) and then returned to the original level, forming a previously observed U-shaped curve. The initial fall in basal FSH level was not followed by a return to pretreatment level. These changes were accompanied by an exponential increase of more than 3-fold in the PL levels. The bidirectional pattern of LH release was associated with parallel changes in pituitary sensitivity to a 10-mcg pulse of LRF. Pituitary reserve, defined as the response to the 2nd and 3rd pulses of LRF, exhibited unidirectional augmentation. This progression in PL release upwards was unaccompanied by changes in pituitary PL sensitivity and reserve. The contribution of hypothalamic LRF and dopamine in the participation of these functional changes of LH, FSH, and PL are discussed.^ieng

Steroid sex hormones and prolactin in postmenopausal women with generalized mammary carcinoma during prolonged dexamethasone treatment.

The endocrine response to prolonged dexamethasone treatment was investigated in six postmenopausal women with generalized mammary carcinoma. Plasma cortisol levels decreased rapidly and became undetectable whereas significant concentrations of plasma dehydroepiandrosterone and androstenedione persisted throughout the study, even in two ovariectomized patients, indicating a certain degree of autonomy or a greater resistance of adrenal 'androgens' to the inhibition of ACTH secretion. Except in the ovariectomized patients, plasma testosterone did not fall significantly whereas the plasma oestrogens tended progressively towards undetectable concentrations. A similar response was found in six normal postmenopausal women although the disappearance of their oestrogens was relatively rapid. This indicates that much of the testosterone present after the menopause could still be produced by the ovaries whereas the ovarian production of oestrogens becomes negligible. The delayed disappearance of oestrogens in the patients with mammary carcinoma indicates that the persisting adrenal 'androgens' remained efficient precursors of oestrogen synthesis within the peripheral tissues and presumably within the mammary tumour itself. Plasma dihydrotestosterone behaved like the plasma oestrogens. Despite the fall in plasma oestrogens, plasma gonadotrophins did not increase further but plasma prolactin rose progressively. The persistance of steroid sex hormones and the rise of plasma prolactin might explain the poor response to dexamethasone treatment in mammary carcinoma.

PIP: A prolonged suppression of the adrenal cortex was produced by giving dexamethasone to 6 postmenopausal women with generalized mammary carcinoma. Plasma cortisol levels decreased rapidly while plasma dehydroepiandrosterone and androstenedione persisted. Plasma testosterone did not fall, except in ovariectomized patients. Plasma estrogens gradually decreased. This slow disappearance of estrogen indicated that persisting adrenal androgens continued to be precursors of estrogen synthesis in peripheral tissues, and possibly within the tumor tissue also. Plasma dihydrotestosterone estimations were similar to those of plasma estrogens. Plasma gonadotropins remained the same. Prolactin increased gradually. Since the growth of mammary carcinoma in postmenopausal women may be partially under endocrine control and the hormones involved are the sex hormones, and possibly prolactin, the persistence of sex hormones and rise of plasma prolactin may be why dexamethasone produces only a minimal response.

Steroid and prostaglandin concentrations in the plasma of pregnant ewes during infusion of adrenocorticotrophin or dexamethasone to intact or hypophysectomized foetuses.

Catheters were implanted into 16 ewes and their foetuses between days 110 and 124 of gestation. Hypophysectomy was attempted in eight of these foetuses. Continuous infusion of synthetic ACTH (10 microgram/h) or dexamethasone (1mg/24 h) into the foetus, starting between days 124 and 129, induced premature parturition. The concentration of progesterone in the maternal peripheral plasma decreased before parturition in all animals while the level of oestradiol increased in ewes with intact foetuses or in those in which hypophysectomy was incomplete. When hypophysectomy was complete, no increase in the maternal level of oestradiol occurred before delivery. The concentration of 13,14-dihydro-15-oxo-prostaglandin F2alpha increased in the peripheral plasma of ewes with intact or hypophysectomized foetuses infused with ACTH. It is suggested that an intact foetal pituitary gland is required for the rise in the level of oestrogen prepartum, but that this rise is not essential for increased prostaglandin production of parturition.

PIP: The effectiveness of dexamethasone or adrenocorticotrophin (ACTH) in inducing parturition in the hypophysectomized fetus of the ewe was investigated. 16 cross-bred ewes were used. In 8 hypophysectomy was attempted between Days 110-120 of pregnancy. Dexamethasone or ACTH were infused into a fetal vein from Days 124 to 129 of pregnancy until delivery occurred. Progesterone, estrone, and estradiol were measured by radioimmunoassay. Cortisol was measured by competitive protein binding or radioimmunoassay. Prostaglandin (PGFM) was also determined by radioimmunoassay as was ACTH growth hormone and prolactin. The interval from the start of the infusion to delivery in fetuses adminstered dexamethasone was the same whether they were intact or hypophysectomized. The induction-delivery interval was significantly longer in the hypophysectomized fetuses administered ACTH. Hypophysectomized fetuses were less viable than intact ones. Premature delivery following infusion in the intact fetus resulted in a decrease in progesterone in maternal plasma and an increase in estradiol. In maternal plasma of intact fetuses PGFM increased in the last 20-30 hours before delivery when ACTH was infused. Differences between intact and hypophysectomized fetuses in concentrations of progesterone in the maternal plasma and in the cortisol levels were insignificant. When hypophysectomy was complete the estradiol level was without the increase seen in intact fetuses. The results suggest that an intact fetal pituitary gland is required for the rise in the level of estrogen prepartum, but that this rise is unessential for increased PGFM production and parturition.

Quantitative comparison of prolactin production by decidua compacta and spongiosa from the first trimester elective termination of pregnancy.

Prolactin (PRL) producing capacity was studied in explants of decidua compacta and decidua spongiosa obtained from 41 patients undergoing termination of pregnancy at gestation 6 to 12 weeks. In vitro PRL producing capacity, expressed as mIU/g protein, of the decidua compacta was significantly higher (P < 0.05) than those of decidua spongiosa. Production of PRL increased with gestation from 6 to 12 weeks with a more rapid rate at the later gestation. The pattern of increase fitted significantly (P < 0.0001) to the exponential model for both decidua compacta and decidua spongiosa. The exponential regression equations for decidua compacta and decidua spongiosa were (ln y = 4.25 + 0.19x) and (ln y = 2.80 + 0.31x) respectively. Hence, although both decidua compacta and decidua spongiosa had a similar pattern of increase in PRL production, the rate of increment was significantly greater in decidua spongiosa than in decidua compacta. These findings suggest that separating decidua compacta and decidua spongiosa of the first trimester would reduce the heterogeneity of decidual tissue and offer a new approach to the studies of the synthesis, release and regulation of PRL production by human decidua.