hCG Challenge Research Articles

Differential action of decidual luteotropin on luteal and follicular production of testosterone and estradiol.

Decidual tissue of the rat produces a hormone with physiological and biochemical characteristics similar to those of PRL. Because PRL affects both follicular and luteal production of testosterone and estradiol, it was of interest to determine whether decidual luteotropin affects basal and/or LH-stimulated ovarian secretion of steroids and whether it differentially affects follicular and luteal synthesis of testosterone and estradiol. The uteri of pseudopregnant adult rats were scratched on day 5 to induce decidual tissue formation. Pseudopregnant animals without decidua were used as controls. Rats were either hypophysectomized on day 8 or left intact. They were treated with 1.5 IU hCG/day or with vehicle between days 8-9. On day 9, blood was obtained from the ovarian vein, and both corpora lutea and large antral follicles were isolated and incubated in vitro. The presence of the decidua significantly suppressed both basal and hCG-stimulated ovarian secretion of estradiol, yet enhanced progesterone production. A similar inhibitory effect of decidual tissue on hCG stimulation of testosterone and estradiol was observed in the hypophysectomized rats. When the effect of decidua on follicles and corpora lutea was studied separately, it was found that follicles of rats with decidua produced significantly less testosterone and estradiol than follicles of rats without decidua. hCG administration to either intact or hypophysectomized rats markedly enhanced the follicular capacity to produce these two steroids. However, the degree of hCG stimulation of follicular steroidogenesis was significantly reduced by the presence of decidual tissue. In contrast, the decidua did not inhibit the in vitro steroidogenic capacity of corpora lutea. Luteal tissue of intact rats with or without decidua produced similar basal amounts of testosterone and estradiol and responded to a hCG challenge with comparable increases in the production of both steroids. After hypophysectomy, however, the responsiveness of corpora lutea to hCG stimulation differed in rats with or without decidual tissue. Whereas luteal cells of rats without decidual tissue gradually lost their responsiveness to hCG stimulation, luteal cells of rats with decidua remained highly responsive to hCG and produced high levels of testosterone and estradiol. In summary, the present investigation demonstrates that decidual luteotropin impairs ovarian secretion of estradiol and significantly inhibits the stimulatory effect of hCG on ovarian secretion of testosterone and estradiol.(ABSTRACT TRUNCATED AT 400 WORDS)

Effect of alpha-chlorohydrin on metabolism and testosterone secretion by rat testicular interstitial cells.

The direct effect of alpha-chlorochydrin (alpha-CH) on basic metabolism (glucose utilization and oxygen consumption) and testosterone secretion by isolated rat interstitial cells (I-cells) has been studied. In the range of concentrations between 5 and 100 microliter/ml, only the highest doses of alpha-CH decreased cell vitality and their histochemical stain for 3 beta-HSD. Oxygen consumption of I-cells was depressed at all doses higher than 10 microliter/ml and this effect was reversible only with doses lower than 50 microliter/ml. glucose utilization by I-cells was depressed significantly by alpha-CH and this effect was particularly dramatic with doses higher than 50 microliter/ml. alpha-CH decreased testosterone secretion by I-cells, with maximal effects at 100 microliter/ml. I-cells responded to hCG challenge by increasing testosterone secretion, and hCG prevented the toxic effect of alpha-CH at the lowest dose (10 microliter/ml) of alpha-CH, but failed to overcome the effects of a high dose (100 microliter/ml).

496 PULSATILE GROWTH HORMONE (GH) SECRETION DURING PUBERTAL DEVELOPMENT IN INTACT AND CASTRATE MONKEYS

To assess whether pulsatile GH secretion changes during pubertal development, 23 intact and 21 castrate male macaques (rhesus and cynomologous) from prepubertal through adult life were evaluated. Blood was withdrawn at 15 min intervals for 12 or 24 hr through a femoral venous catheter. All animals were fit with a mobile vest and tether assembly. Pubertal development was assessed on the basis of chronological age, gonadotropin and testosterone secretion, testicular volume, hCG challenge tests and skeletal age. The pulsatile secretory GH data are summarized below: These data suggest that pulsatile GH secretion does not change significantly during pubertal development in male monkeys and that endogenous testosterone does not alter pulsatile GH secretion.

Contrasting effects of prolactin on luteal and follicular steroidogenesis.

To determine whether prolactin affects both luteal and follicular production of testosterone and oestradiol, pseudopregnant rats, either intact or hypophysectomized on day 8, were injected daily between days 8 and 9 with 1.5 i.u. human chorionic gonadotrophin (hCG), 250 micrograms prolactin or a combination of both. Control rats were given vehicle. On day 9, blood was obtained from the ovarian vein and corpora lutea and follicles were isolated and incubated in vitro for 2 h. Administration of hCG to intact rats increased ovarian secretion of testosterone and oestradiol dramatically, but did not affect progesterone secretion. Hypophysectomy on day 8 of pseudopregnancy was followed by a drop in ovarian steroid secretion. Prolactin treatment of hypophysectomized rats markedly enhanced progesterone production but had no stimulatory effect on either testosterone or oestradiol. In contrast, hCG dramatically enhanced ovarian secretion of both testosterone and oestradiol without affecting progesterone secretion. Prolactin administered together with hCG antagonized the stimulation of both testosterone and oestradiol secretion by hCG, yet increased progesterone production. When the specific effects of hCG and prolactin administration on follicles and corpora lutea were studied separately, it was found that hCG treatment in vivo greatly stimulated testosterone and oestradiol production by both tissues in vitro. Since hCG only marginally affected aromatase activity in the follicle, had no effect on aromatase activity in luteal cells and did not increase progesterone synthesis, it appears that hCG acts to increase the formation of androgen substrate for oestradiol biosynthesis. Prolactin, administered with or without hCG, inhibited both basal and hCG-stimulated testosterone and oestradiol synthesis by the follicle. In sharp contrast to its inhibitory effect on follicular production of steroids, prolactin appears to be essential for LH stimulation of testosterone and oestradiol by the corpus luteum. In the absence of prolactin, luteal cells gradually ceased to respond to LH and decreased their output of testosterone and oestradiol. Prolactin administration to hypophysectomized rats did not affect luteal cell production of either steroid. However, corpora lutea of rats treated with prolactin responded to the hCG challenge with an increase in testosterone and oestradiol synthesis. In summary, results of this investigation demonstrate that prolactin affects follicular and luteal production of testosterone and oestradiol in opposite ways.(ABSTRACT TRUNCATED AT 400 WORDS)

Activity of LH receptor, LH-stimulated cyclic AMP and testosterone production in the Leydig cell of heat-acclimatized rats.

Key reactions associated with the capacity of the isolated Leydig cell to synthesize testosterone were studied in male rats acclimatized to a hot environment (33-35 degrees C, 25-40% relative humidity) and controls (20-22 degrees C, 30-50% relative humidity). The results demonstrate that acclimatization to heat coincides with: (1) a lower number of human chorionic gonadotrophin (hCG) receptors (P less than 0.01) in the Leydig cell, (2) higher affinity of the Leydig cell for hCG (P less than 0.05), (3) lower hCG-stimulated cyclic AMP production (P less than 0.05) by the Leydig cell and (4) lower capacity of the Leydig cell to synthesize testosterone (P less than 0.01) after hCG challenge. It is suggested that the major cellular alteration responsible for the decreased testosterone secretion by the Leydig cell lies distal to the step involving the binding of the trophic hormone to its receptor and that heat-acclimatization induces changes in the integrity of the various cellular membranes leading to the impeded function of adenylate cyclase and 17 beta-hydroxysteroid oxidoreductase.

Male sexual development in the monkey. I. Cross-sectional analysis of pulsatile hypothalamic-pituitary-testicular function.

Pulsatile secretion of serum gonadotropins and testosterone was studied in 46 monkeys of varying ages from 9 days of age through adult life. Although some of the hormonal analysis was longitudinal in nature, most comparisons were cross-sectional. On the basis of pulsatile secretory patterns, hCG and GnRH stimulation, skeletal age, testicular volume, and histology, we have arbitrarily defined four developmental age groups: postnatal (less than 7 months), prepubertal or juvenile (7-27 months), pubertal (28-59 months), and adult (greater than or equal to 60 months). In accomplishing the pulsatile studies, blood was withdrawn at 15-min intervals over 24 h without anesthesia using a mobile vest and tether assembly to support an indwelling cannula. GnRH and hCG challenge tests were done on one or more occasions on all animals. Plasma samples were analyzed for concentrations of FSH, LH, testosterone, dihydrotestosterone and delta 4-androstenedione by established RIAs and an in vitro bioassay for LH. During the frequent sampling period of 24-h duration for all except postnatal animals, testosterone pulses of large amplitude (up to 8-fold) occurred in postnatal, pubertal, and adult animals. Pulsatile gonadotropin secretion was seen at all ages; however, the highest pulses (up to 15-fold) occurred in prepubertal animals even though this was an infrequent occurrence. Time series analysis techniques were applied for objective statistical characterization of cyclic patterns. Basic rhythms corresponding to 50- to 90-min frequency cycles in gonadotropin secretion were identified. Substantive differences between LH concentrations by bioassay and RIA were seen infrequently. Our findings illustrate that: 1) circulating gonadotropin and testosterone pulses change in amplitude but not necessarily frequency during pubertal development, and 2) primate models are a useful paradym for the longitudinal study of human male sexual development. We conclude that where direct human investigation may be limited, much can be learned by study of these primate surrogates.

Testicular responsiveness to a single dose of hCG during chronic hyper- and hypoprolactinemia in aged men.

In order to characterize the long‐term effects of elevated or lowered serum prolactin levels on testicular endocrine function, peripheral serum FSH, LH, prolactin, testosterone, 17‐hydroxyprogesterone, and estradiol concentrations were determined in hyper‐ and hypoprolactinemic men (treated with neuroleptics versus dopamine agonists), 50 to 80 years of age, in the basal state and after a single intramuscular injection of 5000 IU hCG. Prior to hCG injection, the concentrations of testosterone and 17‐hydroxyprogesterone were significantly lower in hyper‐ than in hypoprolactinemic men (P < 0.02); but estradiol, LH, and FSH levels were not significantly different between the two groups investigated. In hyperprolactinemic men, hCG induced a significant increase (196 ± 40%, SE,P < 0.05) in the mean maximum serum testosterone concentration at 2 to 4 days; whereas in the hypoprolactinemia group, the maximum androgen response was 162 ± 11%. The significant androgen response seen during chronic hyperprolactinemia was associated with a smaller increase in estradiol concentration (274 ± 44% versus 472 ± 78%, P0.05) at 1 to 2 days after hCG injection as compared with the hypoprolactinemia group. The behavior of 17‐hydroxyprogesterone was similar in both groups. Following hCG injection, serum FSH showed a tendency to decrease in both groups.The present results suggst differences in testicular function during hyper‐ and hypoprolactinemia, and indicate that prolactin may regulate testicular androgen synthesis at several steps. In the basal state (before hCG administration), testosterone output of hyperprolactinemic men appears to be reduced by inhibition of one or more steps, as yet unidentified, in the biosynthetic pathway proximal to C21 steroid side‐chain cleavage. During hCG challenge, however, partial inhibition by hyperprolactinemia of testicular aromatization may offer an explanation for the major testicular androgen response to gonadotropin stimulation, when compared with the low pretreatment levels of testosterone.

Intraovarian localization of luteinizing hormone/human chorionic gonadotropin stimulation of testosterone and estradiol synthesis in the pregnant rat.

The objective of this investigation was to determine whether LH acts directly on luteal cells to stimulate testosterone and estradiol synthesis or whether it stimulates follicular and/or interstitial production of androgen and thus provides androgen substrate for luteal cell production of estradiol. Pregnant rats were injected with 1.5 IU human CG (hCG) twice daily sc between days 12 and 14. On day 14, blood was obtained from both the jugular and ovarian vein. Corpora lutea (CL), follicles, and interstitium were isolated and incubated at 37 C for 4 h. Estradiol, testosterone, and progesterone levels were measured in the peripheral circulation, ovarian vein plasma, tissues, and medium. After hCG treatment, no ovulation occurred, rats remained pregnant, and progesterone levels in the serum and in the ovarian vein plasma remained unchanged. In contrast, estradiol and testosterone levels in the ovarian vein increased from 0.7 +/- 0.1 and 0.6 +/- 3.4 ng/ml, respectively, in vehicle-treated rats to 12.5 +/- 3.5 and 4.8 +/- 1.4 ng/ml in hCG-treated animals. In vivo treatment with hCG dramatically increased the in vitro capacity of luteal cells to synthesize de novo both testosterone and estradiol but had no stimulatory effect on progesterone synthesis. Testosterone synthesis by CL increased from 21 +/- 4 to 255 +/- 114 pg/CL whereas estradiol synthesis rose from 30 +/- 7 to 4481 +/- 641 pg/CL. hCG also increased follicular synthesis of both estradiol and testosterone. The interstitium responded to the hCG challenge with a 50-fold increase in testosterone synthesis but with no change in estradiol production. To determine whether hCG rapidly stimulates ovarian production of testosterone, both in vivo and in vitro approaches were used. In the in vitro experiments, CL follicles, or interstitium obtained from day 14 pregnant rats were incubated with or without 3 IU hCG. In the in vivo experiments, day 14 pregnant rats were injected with 3 IU hCG iv and were bled from the jugular and ovarian veins 0.5 and 2 h later. No increase in testosterone and estradiol production was observed after a short challenge with hCG. In summary, this study demonstrates that in the pregnant rat a sustained increase in serum hCG activity stimulates ovarian secretion of both testosterone and estradiol. We conclude that LH can act to induce the synthesis and/or activation of enzyme(s) involved in the conversion of progesterone to androgen in luteal tissue. The results also demonstrate that LH stimulates the synthesis of androgens but not of estradiol in interstitial tissue and confirms the finding that LH stimulates follicular production of both testosterone and estradiol.

Testicular responsiveness to human chorionic gonadotrophin in growth hormone deficient pre-pubertal boys: lack of effect of replacement therapy.

The effect of hGH therapy on testicular response to hCG was studied in 7 pre-pubertal boys with known growth hormone deficiency. Each boy received 2000 IU hCG intramuscularly for 3 consecutive days either before starting hGH therapy or 4 months after temporarily discontinuing hGH therapy. A second 3 day series of hCG injections was administered after each boy had received 4 months of hGH treatment. Before each hCG challenge, serum concentrations of testosterone, LH and FSH were obtained and an iv GnRH test was performed. Growth hormone treatment either maintained or established linear growth velocities equal to or greater than expected for the patient's skeletal age. Testicular response off hGH therapy, either maximum serum concentration of testosterone or maximum rise above baseline, was not significantly different than testicular response while on hGH therapy. Testicular responses did not correlate significantly with either basal concentration of gonadotrophins or gonadotrophin responses to GnRH. Despite its effectiveness in stimulating growth, hGH did not effect testicular responsiveness to hCG in pre-pubertal boys with hGH deficiency.

Nature of immune complexes formed in rhesus monkeys immunized with Pr-B-HCG-TT on challenge with hCG

Seven rhesus monkeys with circulating anti-hCG antibodies were challenged on repeated occasions with doubling doses of hCG. The antibody titers declined after hCG challenge. The hormone was completely bound by the antibodies and no evidence for free hCG was available by a) assay for hCG activity in the supernatants after precipitation of the antigen-antibody complexes with polyethyleneglycol (PEG), b) the absence of 125I-hCG peak at the site corresponding to the free hormone in sucrose density gradient runs, coupled with the identification of the entire radioiodinated hCG in the antibody bound region. The hCG-anti-hCG complexes had a sedimentation constant of 175 indicating that a minimum of three IgG molecules were bound per 125I-hCG molecule. No change in the C 3 component of the complement was found in the blood samples removed at different time periods after challenge with hCG. The hCG-anti-hCG complexes separable with graded concentrations of PEG when reconstituted in phosphate buffered saline possessed no biological activity in the Leydig cell bioassay. In three rhesus monkeys, an intravenous injection of hLH was given prior to the hCG clearance test, hLH did not cause a fall in the anti-hCG titers of the type noted with hCG challenge.