Hyperinsulinemia. A link between hypertension obesity and glucose intolerance.

Hypertension and glucose intolerance, determined in a random population sample (n = 2,475), showed a highly significant (P less than 0.001) association from the mildest levels of both conditions, independent of the confounding effects of age, sex, obesity, and antihypertensive medications. Summary rate ratios for hypertension were 1.48 (1.18-1.87) in abnormal tolerance and 2.26 (1.69-2.84) in diabetes compared with normal tolerance. Altogether, 83.4% of the hypertensives were either glucose-intolerant or obese--both established insulin-resistant conditions. Fasting and post-load insulin levels in a representative subgroup (n = 1,241) were significantly elevated in hypertension independent of obesity, glucose intolerance, age, and antihypertensive medications. The mean increment in summed 1- and 2-h insulin levels (milliunits per liter) compared with nonobese normotensives with normal tolerance was 12 for hypertension alone, 47 for obesity alone, 52 for abnormal tolerance alone, and 124 when all three conditions were present. The prevalence of concentrations (milliequivalents per liter) of erythrocyte Na+ greater than or equal to 7.0, K+ less than 92.5, and plasma K+ greater than or equal to 4.5 in a subsample of 59 individuals with all combinations of abnormal tolerance obesity and hypertension was compared with those in 30 individuals free of these conditions. Altogether, 88.1% of the former vs. 40.0% of the latter group presented at least one of these three markers of internal cation imbalance (P less than 0.001). We conclude that insulin resistance and/or hyperinsulinemia (a) are present in the majority of hypertensives, (b) constitute a common pathophysiologic feature of obesity, glucose intolerance, and hypertension, possibly explaining their ubiquitous association, and (c) may be linked to the increased peripheral vascular resistance of hypertension, which is putatively related to elevated intracellular sodium concentration.

Binding kinetics of the long-acting gonadotropin-releasing hormone (GnRH) antagonist antide to rat pituitary GnRH receptors.

The GnRH antagonist Antide has been shown to produce prolonged inhibition of gonadotropin secretion in ovariectomized monkeys and other animal models. The reasons for such a long duration of action have not yet been clarified. To understand the mode of action of this new antagonist, we have performed association and dissociation binding kinetics using either crude rat pituitary homogenates as source of GnRH receptors or dispersed pituitary cells in culture. The binding characteristics of the radioiodinated Antide analog 125I-labeled[D-Tyr0] Antide to GnRH receptors in rat pituitary homogenates were comparable to those of the first generation GnRH antagonist 125I-labeled [Ac(3)Pro1,pFD-Phe2,D-Trp3,6]GnRH or the GnRH agonist 125I-labeled [D-Trp6,(N-Et)Pro9,Des,Gly10]GnRH, with an affinity constant (Ka) in the 10(10) M-1 range. The maximum binding capacity was consistently higher with the antagonist tracers than with the [125I]GnRH agonist. Both antagonists dissociated at a slower rate at 4 C (approximately 4 times) than the [125I]GnRH agonist. Incubation at 23 C of 125I-labeled [D-Tyr0] Antide previously bound at 4 C resulted in complete dissociation within 8 h after the addition of an excess amount of any of the GnRH analogs; in addition, simple dilution of the incubation medium produced spontaneous dissociation at this temperature. Using rat pituitary cells, Antide was found to inhibit the LH response to native GnRH (10(-8) M) in a dose-related manner. To test whether the binding of Antide is normally reversible at 37 C, Antide (10(-7) M) was added to the culture medium 3 days after cell plating, and the initial preincubation was resumed for 24 h. Cells were then washed twice, and dissociation was allowed to take place. Bound Antide was shown to dissociate rapidly at 37 C, as cells previously treated with Antide produced a full LH response within 24 h if challenged with native GnRH. In conclusion, the binding kinetics of 125I-labeled [D-Tyr0]Antide to GnRH receptors, which should reflect those of Antide, did not present abnormal features. Although this antagonist, similar to other GnRH antagonists, dissociated from pituitary receptors at a slower rate than GnRH analogs, rapid and spontaneous dissociation was achieved at 23 C with simple dilution, and dissociation of unmodified Antide occurred at 37 C. Taken together, our results support the concept that the long duration of action of Antide is not due to any toxic effect of Antide at the receptor site and could derive only marginally from the slow dissociation rate of this antagonist.

Plasma growth hormone (GH) response to intravenous GH-releasing factor (GRF) in adult rats: evidence for transient pituitary desensitization after GRF stimulation.

The ability of human (h)GRF-(1-29)NH2 to stimulate GH secretion was studied in cannulated adult rats. In order to suppress endogenous GRF secretion and the inhibitory action of hypothalamic somatostatin (SRIF), rats were anesthetized with sodium pentobarbital. Intravenous administration of hGRF-(1-29)NH2 elicited a dose-dependent response of plasma GH, with 250 ng/kg being the smallest effective dose in male rats. In female rats, for each dose tested (250 to 70,000 ng/kg), the GH response represented only about 60% that of male rats. Repeated iv stimulations with hGRF-(1-29)NH2 at short time intervals (45 min) produced transient desensitization of pituitary responsiveness to GRF: a blunted GH response to the second and third stimulations was observed both in male and in female rats and for each dose tested. Similar blunted responses were also obtained with repeated injections of native hGRF-(1-44)NH2. The possibility that these blunted responses could be due to incomplete suppression of hypothalamic SRIF secretion by sodium pentobarbital was excluded by the use of rats that were passively immunized against SRIF; in these rats, it was shown that at least 65% of the inhibition of the GH response after the second GRF stimulation was unrelated to SRIF action. Similar transient desensitization to repeated hGRF-(1-29)NH2 stimulations was also observed in conscious rats that were passively immunized against SRIF. This occurrence of blunted responses was shown to be related to the length of the time interval between GRF stimulations, with longer intervals resulting in less or no desensitization. It appears thus that modulation of pituitary responsiveness to the action of GRF is mediated by at least two independent mechanisms in the rat: in addition to the inhibitory action imposed by hypothalamic SRIF, which induces periods of refractoriness to the action of GRF, it was shown in this study that in the pituitary level each GRF stimulation also induces a transient desensitization of somatotrophs for about 1 h. This period of refractoriness might not be due to excessive stimulation with GRF, since it was also observed with the lowest dose of hGRF-(1-29)NH2 that gave a significant release of GH. Finally, a sex difference was confirmed for the response of anesthetized adult rats to stimulation with hGRF-(1-29)NH2, reflecting a sex steroid-induced modification of pituitary responsiveness to GRF stimulation.

Growth hormone (GH) deprivation induced by passive immunization against rat GH-releasing factor delays sexual maturation in the male rat.

GH deprivation after passive immunization against rat GRF (rGRF) markedly affects somatic growth in male rats. Since it has been postulated that GH and probably insulin-like growth factor-I (IGF-I) might have a permissive role on sexual maturation, the effects of GH deprivation on the course of sexual maturation were tested. Male rats were treated with a potent anti-rGRF serum between 15 and 39 days of life (0.25 ml administered sc every second day). Body weight of treated rats averaged 62% of that of control (normal rabbit serum-treated) rats at 40 days of life (d), and 64% at 50 d after which age, treated rats started to grow normally. At 40 and 50 d, pituitary GH content was very much depressed (representing approximately 20% of control values at both ages), plasma GH was undetectable, and plasma IGF-I levels averaged 30% of those of control rats. At 70 d, 30 days after cessation of treatment, pituitary GH content, and IGF-I secretion were almost normal. At 40 d, testes and seminal vesicles of treated rats were small-for-age in agreement with significantly decreased plasma levels of FSH and delayed spermatogenesis characterized by the presence of only few or no spermatozoa. At 50 d, 10 days after cessation of anti-rGRF injections, progress of sexual maturation was found to be consistent with age and coincided with normalization of growth rate. At 40 and 50 d, pituitary contents of FSH and LH were severely decreased but became normal at 70 d. In conclusion, GH deprivation which markedly affected somatic growth induced a transient delay of sexual maturation. GH deficiency seems to have affected mostly the synthesis and secretion of FSH, thus producing a delay in testes growth and in the differentiation of the germinal cells. The low levels of IGF-I might also have been the cause for the delay of maturation at the pituitary and/or the gonadal levels.

Enhanced response of plasma aldosterone to metoclopramide in essential hypertension.

Aldosterone responses to posture and the dopamine antagonist, metoclopramide, were studied in seven normotensive controls and 12 patients with essential hypertension. Both groups had similar basal supine plasma renin activity and aldosterone levels. Aldosterone levels of the hypertensive patients were greater than those of the controls 10 min after assuming an upright posture but indistinguishable at 120 min. Metoclopramide induced a peak fourfold increase above basal aldosterone levels in the hypertensive group as compared to a peak twofold increase observed in the normotensive controls. Mean 120-min integrated aldosterone response area for the hypertensives (237 +/- 44 10(-10) mol min/l) was greater (P less than 0.05) than that for normotensive subjects (106 +/- 32 10(-10) mol min/l). Simultaneous cortisol, plasma renin activity, and serum potassium levels were unaffected by metoclopramide. It is concluded that dopaminergic modulation of aldosterone secretion may be altered in essential hypertension.

Histochemical demonstration of delta5-3beta-hydroxysteroid dehydrogenase activity in ovaries of intact infant mice and mice treated with anti-rat gonadotropin.

The localization of delta5-3beta-hydroxysteroid dehydrogenase activity was demonstrated histochemically in the neonatal mouse ovary. Histochemical studies were also undertaken in an attempt to investigate the effects of gonadotropic deprivation from birth to age 7 or 14 days on the distribution of enzymatic activity. Between birth and the age of 2 weeks, delta5-3beta-hydroxysteroid dehydrogenase activity was observed in virtually all follicles. In the newborn mouse ovary, the activity was found in granulosa cells of follicles developing in the center of the organ. On the 14th day, the granulosa cells of some apparently normal follicles histochemically were relatively inert, while others, obviously atretic, demonstrated extensive, localized, diformazan granules. Deprivation of endogenous circulating gonadotropin by daily injections of anti-rat gonadotropin had specific effects on follicular development and histochemical patterns in animals deprived of gonadotropins for 14 days but not for only 7 days.

Neural tube defects after infertility treatment: a review.

OBJECTIVE: To investigate whether an association exists between ovulation induction and neural tube defects (NTDs). MATERIALS AND METHODS: Risk estimations in the medical literature were identified through Medline, and validity and power were assessed. Large in vitro fertilization-embryo transfer (IVF-ET) registries represent another source of information. The total number of NTDs and the total number of fetuses were computed from five registries. These data were expressed as proportions and compared with data from the general population. RESULTS: Only one study could be identified as both valid and powerful, through literature review. This case-control study concluded there was no association between ovulation induction and NTDs. The pool of IVF-ET registry data represents another powerful epidemiologic tool. Analysis of the registry data confirms the findings of the case-control study. CONCLUSIONS: Ovulation induction does not seem to represent a risk factor for NTDs in the offspring.

Hormonal and clinical responses in amenorrhetic patients treated with gonadotropins and a nasal form of synthetic gonadotropin-releasing hormone.

Synthetic gonadotropin-releasing hormone (GnRH) in the form of nasal drops was self-administered by five amenorrheic patients in an attempt to assess its therapeutic value in anovulatory infertility. After follicular maturation had been induced with human menopausal gonadotropins (HMG), a total daily dose of 7.5 mg of GnRH in the form of nasal drops was self-administered at 2-hour intervals for 6 hours on 3 consecutive days. In four patients, plasma luteinizing hormone (LH) levels were significantly elevated over a period of at least 8 hours. In three of these patients, in addition, there was a definite upward shift in the basal body temperature (BBT) curve, and uterine bleeding occurred 6 to 9 days after the first dose of GnRH. In the fourth patient, ovulation was induced as indicated by a biphasic BBT curve, a plasma progesterone level of 13 ng/ml, and a luteal phase of 15 days. In the remaining patient, there was a borderline LH response and no clinical response. It is concluded that GnRH, in the form of nasal drops, is effective in eliciting and maintaining elevated plasma LH levels in patients in whom follicular maturation has been induced with HMG. By obtaining ovulatory LH levels, such a regimen can lead to ovulation. In addition, intranasal self-administration of GnRH is convenient and may provide an alternative route of administration for long-term therapy with this hormone.

Treatment of cryptorchidism with a potent analog of gonadotropin-releasing hormone.

Pernasal therapy of cryptorchidism with D-Leu6-des-Gly10-gonadotropin-releasing hormone ethylamide (D-Leu6-des-Gly10-GnRH-EA), a potent, long-acting GnRH analog, was attempted. Eleven prepubertal cryptorchid boys received between 25 microgram once daily and 25 to 50 microgram twice daily for 5 to 12 weeks. Complete testicular descent was achieved in 4 of the 11 boys. GnRH tests (1.5 microgram/kg intravenously), conducted in six boys before treatment, after 4 weeks of treatment, and in 2 boys 3 months after treatment, did not reveal changes in gonadotropin secretion indicative of precocious puberty or of decreased hypophyseal sensitivity to GnRH. Antibodies to the GnRH analog or to GnRH could not be detected.

Excretion of total estrogens and estrone-3-glucuronide during treatment with human menopausal gonadotropins.

HMG treatment is usually monitored by the evaluation of the cervical mucus, the determination of plasma 17 beta-estradiol, total urinary estrogens, ultrasonographic evaluation or a combination of these. We evaluated the daily validity of estrone-3-glucuronide excretion in urine as an indicator of follicular growth and maturation in 28 infertile women who were treated with HMG (Pergonal 500). Total urinary estrogens and estrone-3-glucuronide were measured in 24 h urine collections, and 11 of the women collected the early-morning urine separately. This allowed comparison of the concentrations and excretion of total estrogens and estrone-3-glucuronide of the 24 h urine with that found in the urine collected overnight. This comparison was made on 83 urine samples. The correlation between either the total excretion per 24 h or the concentration per liter in the 24 h urine collection of the two systems of determination was good in all determinations. Also in the urine collected on the day prior to HCG administration, total estrogens measurement was in good correlation with the estrone-3-glucuronide. However, there was statistically a significant difference in the concentrations of total estrogens and estrone-3-glucuronide between the women who ovulated and those who did not. Estrone-3-glucuronide, when calculated as a percentage of the total estrogens, was 60.86% in the women who ovulated and 33.15% in those who did not. These results demonstrate that although estrone-3-glucuronide reflects ovarian function in women treated with HMG, it may serve as a better predictor to ovulation.

Adrenal response to adrenocorticotropin stimulation in unexplained infertile women.

The response to a rapid intravenous administration of adrenocorticotropin (ACTH, cortrosyn) was compared in 24 unexplained infertile women and 13 fertile women. There was no significant difference in the response to a rapid ACTH stimulation as expressed by the slope of testosterone (T) response in both groups. However, the individual and mean T values prior and following the stimulation were significantly higher in the infertile group (P less than 0.001; P less than 0.005, respectively). There was no significant difference in individual values as well as in mean basal values or in mean values of 17-hydroxyprogesterone (17-OHP) after the stimulation between the two study groups (P less than 0.3; P less than 0.9, respectively). There was no significant difference in individual values as well as in mean values of dehydroepiadnrosterone (DHEA) before or 90 min after the stimulation between the two study groups (P less than 0.1; P less than 0.2, respectively). It can therefore be concluded that the elevated basal testosterone values in the infertile group originated from the ovary. Despite the fact that no attempt was made to reduce androgen values 7 (46.66%) of 15 infertile women who were available for follow-up and treatment conceived following ovulation induction therapy.

Clinical, endocrine and ultrastructural study of XY gonadal dysgenesis. A case report.

About 120 cases of XY gonadal dysgenesis have been reported on. We treated such a patient with bilateral gonadectomy. The gonadal tissue's capacity to respond to hormonal trophic stimulation was assessed. When the gonads were examined ultrastructurally, structures with the morphologic characteristics of stromal ovarian cells, Sertoli's cells and Leydig's cells were found. Because of the potential malignancy of the XY gonads, bilateral gonadectomy and hormonal substitution therapy are recommended for these patients. We prefer to use combined hormone replacement with sequential estrogen and progesterone rather than sequential unopposed estrogen because of the small but increased risk of endometrial hyperplasia and carcinoma after long-standing sequential therapy.

The effect of sex steroids on pituitary responsiveness to gonadotropin releasing hormone.

PIP: The direct effect of steroids on rat pituitaries, as reflected by their response to the hypothalamic gonadotropin-releasing hormone (GnRH), was studied in rats. Also, the modulating effect of steroids was investigated in women with primary amenorrhea due to hypothalamic failure. In the human cases, the pituitary was considered as not being regulated by endogenous gonadotropin-releasing hormones and any steroidal effects could be ascribed as being exerted directly on the pituitary gland without being mediated via the hypothalamus. The ovaries of these patients were capable of steroid secretion when stimulated by exogenous gonadotropins. The response to GnRH was evaluated prior to and at different phases of the cycles of ovarian stimulation. Techniques used in the in vitro rat studies are described. Estradiol had a dual effect depending on the dose. Progeste rone had no effect on the base level secretion of either luteinizing hormone (LH) or follicle stimulating hormone (FSH) or on the stimulatory effect of GnRH. However, the addition of progesterone to estradiol counteracted the sensitizing effect of estradiol. In the human cases, dynamic stimulating tests were done to localize the origin of the hormon al insufficiency and to exclude pituitary and ovarian unresponsiveness t o appropriate stimuli. None responded to clomiphene citrate but all had a pituitary response to GnRH and an ovarian response to human menopausal gonadodtropins. In Phase 1 in the absence of ovarian steroids, GnRH evoked an increase in both LH and FSH. In Phase 2, when the endogenous level of estradiol was high, GnRH did not induce FSH release. Elevation of LH secretion was prolonged and reached higher values at the time of increase in the plasma progesterone. In Phase 3, the luteal phase, GnRH failed to elicit either LH or FSH release. It seemed that estrogen sensitized the pituitary to respond to GnRH with a selective augmentatio n of LH secretion. Therefore, it is thought that steroids can modulate pituitary responsiveness to hypothalamic stimuli.^ieng

Diet and weight loss: their effect on norepinephrine renin and aldosterone levels.

The effect of low calorie diet on blood pressure, catecholamines, plasma renin activity (PRA) and aldosterone was examined in 22 obese subjects (19 hypertensives and 3 borderline hypertensives). A significant decrease in blood pressure (P less than 0.05) was observed in all patients after 10 days on the diet. Twenty subjects showed a significant decrease in norepinephrine (NE) levels (P less than 0.05) and two patients showed an extreme increase in NE level. On reexamination six months later these two patients presented with high NE levels and predict blood pressure levels despite having lost 15 and 18 kg respectively. The study group showed a significant decrease in mean PRA (P less than 0.05). A correlation was observed between changes in NE levels and PRA (r = 0.42, P less than 0.05) and between changes in PRA and aldosterone (r = 0.54, P less than 0.05). The reduction in blood pressure associated with caloric restriction in these obese patients may be a result of reduced sympathetic nervous system activity.

Hormonal dependence of the first spermatogenic wave in the mouse.

Antiserum to rat gonadotropins (arG) has been proved capable of binding homologous luteinizing hormone (LH) and follicle stimulating hormone (FSH) in vitro and mouse LH and FSH in vivo. The administration of arG did not evoke antibody production. The physiological role of endogenous gonadotrophins during neonatal life was studied by administration of this antiserum to groups of newborn male mice. Daily injection of arG from birth up to the age of 100 days inhibited markedly weight increase of testes and accessory glands. Histological evaluation of the testes of such treated animals revealed that spermatogenesis up to the stage of pachytene spermatocytes can proceed in the absence of endogenous gonadotropins; however, no spermatids were formed and the number of cells that developed in the hormone-deprived animals was significantly lower than in the normal animal. Substitution treatment with exogenous FSH permitted the formation of a small number of spermatids, but completion of spermatogenesis was obtained only with combined LH and FSH treatment.

The function of the growing follicle.

The follicle plays a major role in the dual function of the ovary--oocyte maturation and release and steroidogenesis required for regulating its own growth and providing the proper environment in reproductive organs for the transport of gametes and nidation. Some aspects of how follicles attain their functional competence following a series of developmental changes are discussed. The presentation is based on data obtained mainly in rodents in which follicular development occurs postnatally. The peak activity of follicular growth occurs during the 1st week of life, but not until the 5th day is follicular development clearly dependent upon gonadotrophin stimulation. The formation of the theca layer and zona pellucida, differentiation of the vascular system and competence to respond to gonadotrophins are acquired during the 2nd week. FSH alone is primarily responsible for granulosa cell proliferation and the integrity of the granulosa cell membrane, but has little differential effect on steroidogenic enzymes. Synergism of FSH and LH promotes an enrichment of the theca layer, enhancement of vascular development and antrum formation, and induces a marked differential stimulation of 20alpha-hydroxysteroid dehydrogenase, aromatizing and cholesterol side-chain cleavage systems. The number of gonadotrophin receptors on granulosa and theca cells increases with follicular development. Steroids secreted by the ovary seem to modulate follicular growth, not only by effects upon FSH and LH release but also by a local influence within the ovary. A number of physiological events related to follicular function are explained according to these observations.

Composition of commercial gonadotrophin preparations extracted from human post-menopausal urine: characterization of non-gonadotrophin proteins.

Gonadotrophin preparations extracted from post-menopausal urine are of low purity and the major protein components are not gonadotrophins. A study was undertaken to identify some of these non-gonadotrophin proteins present in the extracted human urinary gonadotrophin preparations that are commercially available, i.e. Humegon (Organon), HMG Massone (Massone), Metrodin (Serono), Metrodin HP (Serono), Pergonal (Serono) and Progonadyl (Elea). As revealed by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) with Coomassie blue staining and Western blotting analysis, these products had electrophoretic protein profiles which differed in the amounts and species of proteins present. With the exception of Metrodin HP, all the other preparations tested contained tumour necrosis factor binding protein-I, transferrin, and immunoglobulin-related proteins. Some of the products contained in addition: urokinase, Tamm-Horsfall glycoprotein and epidermal growth factor. Recently, a highly purified human urinary follicle stimulating hormone (FSH) preparation (Metrodin HP) became available. In this preparation human FSH represents > 95% of the total proteins (approximately 10,000 IU of FSH/mg of protein). Metrodin HP was demonstrated to be the purest preparation tested, with none of the above-mentioned contaminants detected.

Comparison of pituitary response to regular GnRH, analogue (D-TRP6) and placebo.

Pituitary response to synthetic regular GnRH, to a potent analogue (D-TRp6) and to placebo were compared in ten azoospermic males. FSH and LH were measured prior to and at given intervals following administration of each substance. In addition, plasma levels of testosterone and prolactin were measured. There was no significant difference in the magnitude of FSH and LH release following injection of their the regular or the analogue form of GnRH. However, plasma gonadotrophins remained elevated for significantly longer time periods following the administration of the analogue GnRH. In those patients in whom LH levels remained elevated for at least 24 hours the observation of elevated testosterone levels permitted the inference of adequate biological activity of endogenously produced LH. Patients who did not respond to the regular GnRH were also non-responsive to D-TRp6 GnRH. A surprising finding ws elevated prolactin levels 4-6 hours following GnRH administration. Placebo had no influence on gonadotrophins, testosterone and prolactin.