The effects of testosterone and dihydrotestosterone on hypothalamic regulation of growth hormone secretion.

Testosterone (T) administration to pubertal boys increases spontaneous GH secretion. It is not known whether this occurs via pituitary or hypothalamic mechanisms. We evaluated the GH secretion of 12 boys, aged 13.67 +/- 0.37 yr (mean +/- SE), diagnosed with constitutional delay in growth and adolescence. The evaluation was made both before and after 3 months of treatment with T or the nonaromatizable androgen, 5 alpha-dihydrotetosterone. Serum for determination of spontaneous GH secretion was sampled every 20 min for 24 h. Pituitary responsiveness was assessed by the administration of GHRH with sampling of GH at intervals for the next 2 h. This was also done with pyridostigmine (PDS) pretreatment to assess the effects of somatostatin. The dose of androgen used was 80 mg/m2 month. All tests were then repeated during treatment. Spontaneous GH secretion was analyzed by the Cluster method. The response to GHRH was measured as the area under the curve. Somatostatin effects were quantified as the difference in responsiveness between the two GHRH tests performed at each admission: one without prior PDS administration and one in which somatostatin was blocked by PDS. Treatment with T increased mean spontaneous GH secretion from 2.25 +/- 0.34 micrograms/L before treatment to 6.77 +/- 0.69 micrograms/L (mean +/- SE; P < 0.001) and mean spontaneous peak height from 5.62 +/- 1.05 to 17.21 +/- 1.52 micrograms/L (mean +/- SE; P < 0.001). No significant differences between pretreatment and treatment evaluations for any spontaneous GH secretory parameters were seen in 5 alpha-dihydrotestosterone-treated patients, except that maximum peak height was decreased after treatment (P < 0.02). In T treated patients, the GHRH stimulation tests without prior PDS administration changed from 84.14 +/- 34.54 total micrograms/L before to 102.3 +/- 35.82 total micrograms/L (mean +/- SE; P = NS) after androgen treatment. PDS pretreatment produced an increase in responsiveness to GHRH over the test without PDS pretreatment. This increase was 127.03 +/- 35.68 total micrograms/L before T treatment; after T treatment, this increase was 78.38 +/- 57.6 total micrograms/L (mean +/- SE; P = NS). T treatment, via an estrogen-dependent mechanism, caused increased GH pulse amplitude, thereby increasing the mean serum GH concentration. This increase was not the result of increased pituitary responsiveness or decreased somatostatin tone. This indicates that T exerted its effect on GH via increased GHRH pulse amplitude.

Androgen-stimulated pubertal growth: the effects of testosterone and dihydrotestosterone on growth hormone and insulin-like growth factor-I in the treatment of short stature and delayed puberty.

The purpose of this study was to investigate the roles of androgenic and estrogenic mechanisms in the stimulation of structural growth and plasma GH in male puberty. To resolve these two possible mechanisms, we compared the effect of two androgens in the treatment of constitutional delay in growth and adolescence: an aromatizable androgen, testosterone (T), and a nonaromatizable androgen, dihydrotestosterone (DHT). Nine adolescent males, Tanner stage 1 or 2, were studied before and during treatment with T enanthate (group A) or DHT heptanoate (group B). After 2.5 months of treatment, the height velocity (HV) was 12.6 +/- 2.8 cm/yr (n = 3) in group A and 8.9 +/- 1.7 cm/yr (n = 6) in group B, both within the range of peak HV for pubertal males. In group A, the integrated concentration of GH (ICGH) increased from 3.12 +/- 0.90 to 13.67 +/- 6.0 micrograms/L (P < 0.05), and plasma insulin-like growth factor-I (IGFI) increased from 126.7 +/- 2.5 to 350.3 +/- 20.3 micrograms/L (P < 0.01); plasma T increased from 0.8 +/- 0.5 to 33.8 +/- 11.0 nmol/L (P < 0.001), and the LH response to LHRH decreased from 27.6 +/- 10.7 to 5.9 +/- 2.5 IU/L (P = NS). In group B, ICGH decreased from 4.32 +/- 0.61 to 2.39 +/- 0.42 (P < 0.025), and IGF-I decreased from 218.3 +/- 39.2 to 184.0 +/- 15.8 (P = NS). Plasma T increased from 2.0 +/- 0.5 to 2.7 +/- 0.8 (P = NS), and the LH response to LHRH decreased from 45.7 +/- 14.5 to 10.7 +/- 5.8 (P < 0.05). To further evaluate the mechanism of the effect of DHT on plasma GH, seven male subjects with adolescent gynecomastia were treated with DHT heptanoate, and their responses were studied at 1 week and 3.5 months. ICGH decreased in conjunction with a decrease in the integrated T concentration (r = -0.77; P < 0.001) and to a slight degree with decreasing plasma estradiol (r = -0.39; P < 0.2). Plasma IGF-I did not show a significant change in the subjects with gynecomastia. Thus, the increase in GH at puberty in males appears to be due to an estrogen-dependent mechanism. The suppressive effect of DHT on GH secretion may be due to either suppression of estradiol production or a direct effect. Acceleration of HV into the peak pubertal range by DHT without an increase in plasma GH suggests that an increase in GH is not necessary for the pubertal growth spurt.

Bone mineral density of the lumbar vertebrae in children and adolescents with insulin-dependent diabetes mellitus.

To test the hypothesis that bone mineral density (BMD) is lower in children with insulin-dependent diabetes mellitus (IDDM), we measured BMD of the lumbar vertebrae (L-2 to L-4) by dual-photon absorptiometry in 31 boys and 25 girls, mean age 12.3 years, with IDDM of varying clinical duration (range 0.1 to 14.8 years). Mean standard deviation scores (z scores) were determined for L-2-L-4 BMD, weight, height, weight percentile, and weight-adjusted L-2-L-4 BMD index (L-2-L-4 BMD/weight), with reference data from a previously described white, nondiabetic, age-matched control group (n = 221). Compared with nondiabetic control subjects, male patients with short-term IDDM and all female patients with IDDM did not have significantly different L-2-L-4 BMD, weight, weight percentile, height, or BMD index. Boys with IDDM longer than 1 year had significantly lower weight, weight percentile, and height than did age-matched control subjects. When L-2-L-4 BMD of boys with long-term diabetes was corrected for weight, the L-2-L-4 BMD index was significantly greater than that of control subjects, indicating that weight was disproportionately lower than BMD. There were no significant linear correlations between metabolic control and L-2-L-4 BMD. When L-2-L-4 BMD was adjusted for differences in body weight, spinal BMD values in children with IDDM were not lower than in control subjects. These findings indicate that in children with IDDM, as in previously studied nondiabetic youths, body weight and spinal BMD are highly correlated; although BMD is reduced in some children with diabetes, the reduction parallels reductions in growth, and may simply reflect a normal response of the skeleton to a lower weight-bearing load.

Spinal bone mineral density in 335 normal and obese children and adolescents: evidence for ethnic and sex differences.

Spinal bone mineral density (BMD) and anthropometric measures were studied in 312 nonobese and 23 obese black, white and Hispanic children and adolescents age 5.00-18.99 years. In adolescents BMD correlated with age, weight, height, fat-free density, body mass index, and midarm circumference. Utilizing the entire group of 312 nonobese subjects, mean Z scores were calculated for comparison versus reference subgroups for bone mineral density index (BMDI, BMD/weight). BMDI was greater for black than for white and Hispanic children and adolescents across all ages studied. Female adolescents accumulated spinal mineral more rapidly than male adolescents. Black males had greater mineral than white and Hispanic males. Differences in BMDI between subgroups could not be explained by differences in body weight or spinal vertebral size. BMDI proved a more sensitive measure for comparing subgroups than did BMD. The study provides normative data and a quantitative methodology for analyzing differences in spinal mineral between groups of children and adolescents.

Spinal bone mineral density in children aged 5.00 through 11.99 years.

Lumbar spine (L-2, L-3, L-4) bone mineral density was measured in 184 healthy boys and girls aged 5.00 through 11.99 years by dual photon absorptiometry. Weight, height, age, triceps skinfold thickness, and midarm circumference were also measured. Weight, height, and age were highly correlated with bone mineral density. In the population studied, a quadratic regression equation using body weight as the independent variable best described bone mineral density: bone mineral density = 0.3209 + [0.0168 (weight)] - [0.0001 (weight2)].

Hyperphosphaturia and hypermagnesuria in children with IDDM.

Urinary excretion of calcium, inorganic phosphorus, magnesium, glucose, and creatinine was measured in first-void spot urine samples collected 4 days apart in 220 insulin-dependent diabetic (IDDM) children (mean age 11.9 yr) attending a summer camp. A single control urine sample was obtained from 33 healthy nondiabetic siblings (mean age 11.2 yr). Mean +/- SD urinary calcium-creatinine ratios (UCa/Cr) did not significantly differ between IDDM and control subjects (0.14 +/- 0.09 vs. 0.12 +/- 0.09, respectively, P = 0.156). Mean urinary magnesium-creatinine ratios (UMg/Cr) were elevated in IDDM compared with control subjects (0.15 +/- 0.06 vs. 0.08 +/- 0.03, respectively, P = 0.0001). Similarly, mean urinary phosphorus-creatinine ratios (UP/Cr) were significantly increased over those in control subjects (1.12 +/- 0.33 vs. 0.40 +/- 0.22, respectively, P = 0.0001). UCa/Cr, UMg/Cr, and UP/Cr were correlated with increasing mean urine glucose content (P = 0.0001). No correlations were found when UCa/Cr, UMg/Cr, or UP/Cr were compared with patient age, duration of diabetes, glycosylated hemoglobin, or insulin dosage. Urine losses of phosphorus and magnesium were present even when glycemic control was considered good by several methods (glycosylated hemoglobin, short-term glycemic index, or urinary glucose content). Glomerular hyperfiltration was unable to account for increased urinary mineral content. In conclusion, the data indicate that urinary excretion of phosphorus and magnesium is elevated in children with IDDM, regardless of glycemic control. In the presence of glucosuria, this loss is further enhanced. Urinary calcium excretion is significantly higher only during periods of glucosuria. The data suggest that children with IDDM could be at risk for mineral deficiencies in the absence of intensive insulin management.

Extreme hyperthermia induced in cats by the enkephalin analog FK 33-824.

FK 33-824 [H2N-Tyr-D-Ala-Gly-MePhe-Met(O)-OH] was injected into the third cerebral ventricle of unrestrained cats. Doses of 0.25-4 microgram induced dose-related increases in body temperature. Hyperthermic responses to 1 microgram of the peptide were greater the warmer the environment. Naloxone given intraventricularly 1 hr after FK 33-824 (1 microgram) reduced the hyperthermia. In 12 tests with six cats FK 33-824 (1-25 microgram) increased temperature 4.2-4.7 degrees C. These marked responses were also inhibited by naloxone, but two cats died when administration of antagonist was delayed for 80 min to 3 hr after attainment of maximal body temperature. Larger doses of FK 33-824 (50-250 microgram) evoked little increase in temperature, indicative of a separate action to depress thermoregulation. Although responses to FK 33-824 were antagonized by naloxone, this peptide, like another enkephalin analog D-Ala2-Met-enkephalinamide, must act on receptors which are not affected by morphine since (1) the hyperthermic response to FK 33-824 varied with environmental temperature, whereas the response to morphine does not, and (2) high doses of FK 33-824 depressed thermoregulation, an activity not shared by morphine in the cat. Furthermore, the maximal increases in temperature after FK 33-824 injection were greater than those evoked by either morphine or D-Ala2-Met-enkephalinamide. This observation provides evidence for an additional subset of naloxone-sensitive, v, receptors, stimulation of which can influence thermoregulation in the cat.

Central injection of a sigma opioid receptor agonist alters body temperature of cats.

The prototype sigma opioid receptor agonist N-allyl-normetazocine (SKF 10,047) was injected into the third cerebral ventricle of conscious, unrestrained cats, and their temperature was monitored automatically from the retroperitoneal space. In a cold environment (0 degrees C) a small, but not dose-related, hypothermia occurred after doses of 100-500 micrograms. This response was not antagonized by naloxone given intraventricularly either 15 min before or 1 hr after the opioid. A smaller hypothermia resulted after 250 micrograms SKF 10,047 when the environmental temperature was 22 degrees C, whereas hyperthermia developed in a hot environment (34 degrees C). Thus SKF 10,047 appears to allow body temperature to drift, upward in the heat and downward in the cold, a pattern indicative of thermoregulatory depression. These results are similar to those obtained in the first 2-3 hr after pentazocine administration, and they support a previous classification of the initial temperature response to centrally injected pentazocine as due to stimulation of sigma opioid receptors.

Effects of centrally administered pentazocine and ethylketocyclazocine on thermoregulation in the cat.

The mechanisms for the biphasic response of unrestrained cats to centrally administered pentazocine were examined by injecting 1 mg pentazocine into the third cerebral ventricle at various ambient temperatures (TaS). The initial phase was hyperthermia at Ta = 34 degrees C, but at Ta = 22 degrees C hypothermia, which was enhanced at Ta = 0 degrees C, developed. The second phase was an increase in body temperature that occurred at all three TaS. No evidence was seen of compensatory thermoregulatory effector activity during development of either phase. The first phase can be attributed to general depression of thermoregulation whereas the second phase was likely due to an increase in the level about which body temperature was regulated. Ethylketocyclazocine (250-1000 micrograms) caused a very similar, dose-related change in temperature, neither phase of which, as reported previously for pentazocine, was reduced by a large dose of nalaxone. Thus both agonists appear to act on the same receptors to alter thermoregulation in the cat. These receptors are distinct from the naloxone-sensitive receptors stimulated by morphine.

Thermoregulatory effects of (D-ala2)-methionine-enkephalinamide in the cat. Evidence for multiple naloxone-sensitive opioid receptors.

(D-ala2)-methionine-enkephalinamide (DAME) was injected into the third cerebral ventricle of unrestrained cats. At ambient temperature (Ta) = 22 degrees C, 3.1-50 micrograms caused dose-related hyperthermias. As dosage was increased, the hyperthermias diminished and in some cats hypothermia developed. Hyperthermia was not due to pyrogenic contamination or prostaglandin synthesis since it was not altered by pretreatment with a large IV dose of indomethacin. However, pretreatment with naloxone did cause a dose-related reduction in the hyperthermia. A low dose of DAME (12.5 micrograms) also caused hyperthermia at Ta = 4 and 32 degrees C, indicative of an increase in the level about which body temperature was regulated. On the other hand, a dose of 200 micrograms, which caused hyperthermia Ta = 22 and 32 degrees C, usually caused hypothermia at Ta = 4 degrees C, perhaps due to impairment of thermoregulatory control mechanisms. The response to DAME in the cold was reduced by naloxone pretreatment or reversed by subsequent injection of naloxone. Differences in hyperthermic patterns over a range of TaS and the lack of hypothermogenic action of morphine indicate that DAME alters thermoregulation in the cat by acting on morphine-insensitive, but naloxone-sensitive receptors. Central injection of beta-endorphin (5-50 micrograms) caused a dose-related hyperthermia. (Des-tyr1)-leucine-enkephalin (10-250 micrograms) was weakly hyperthermogenic, and kyotorphin (500 micrograms) did not consistently alter body temperature.