Free alpha-subunit response to gonadotropin-releasing hormone in women with polycystic ovaries

The response of glycoprotein hormone free alpha-subunit to gonadotropin-releasing hormone (GnRH) was evaluated in 12 women with polycystic ovaries (PCOs). Six of these women were premedicated for 3 days with micronized 17 beta-estradiol before receiving a 100-micrograms bolus of GnRH. In nonmedicated PCO patients, GnRH did not significantly alter basal free alpha-subunit levels. In four of the six PCO patients receiving estrogen premedication, a significant increase in free alpha-subunit was observed; these four patients had low progesterone levels at the time of the GnRH test. Among the six premedicated patients, two had elevated (greater than 4 ng/ml) progesterone levels, and the GnRH tests showed no significant effect on the levels of free alpha-subunit. The study revealed a dissociation between the free alpha-subunit responses to GnRH and the responses of luteinizing hormone; a closer relationship was observed between free alpha-subunit and follicle-stimulating hormone responses. It was concluded that the lack of a free alpha-subunit response to GnRH in PCO patients is not due to a primary inability of the pituitary gonadotroph to produce free alpha-subunit but is a consequence of an altered estrogenic milieu, and a free alpha-subunit response to GnRH may reflect the replenishment of both follicle-stimulating hormone and luteinizing hormone in the gonadotrope.

Steroid hormone concentrations in relation to patient prognosis and prostate tumour grade

Survival of patients who received endocrine therapy as first-line treatment for their prostatic cancer was statistically analysed in relation to several parameters, primary tumour stage, metastatic status, age, pretreatment plasma hormone concentrations and Gleason grade. Prognostic indices were derived for both M0 and M1 patients in which Gleason grade and plasma testosterone concentrations were significant prognostic factors. In the M1 patients growth hormone values were also significant and to a lesser degree age. The relationship of Gleason grade to testosterone, growth hormone, prolactin, the gonadotrophins and age was also analysed. No significant differences in any of these hormones was noted with increasing Gleason grade but the age of patients with Grade 5 tumours was significantly lower.

An evaluation of the anti-androgen effects associated with H2 antagonist therapy

The effect of two different H2-receptor antagonists, nizatidine and cimetidine, on sperm counts and hypothalamic-pituitary-gonadal function as determined by responses to provocative gonadotropin releasing factor, GnRH, thyrotropin releasing factor, TRH, and clomiphene were compared to those of men receiving placebo medication. All subjects studied gave informed written consent and were greater than 18 but less than 55 years of age. Sperm concentrations in collected semen specimens, and GnRH and TRH responses before and after 6 weeks of drug exposure were assessed as were the gonadotropin responses to clomiphene while on the drug for an additional 3 weeks. All had normal sperm concentrations and hormone levels before drug exposure and normal responses to both GnRH and TRH. Following drug exposure, the LH response to GnRH and the growth hormone, prolactin, TSH and T4 responses to TRH were similar to those obtained prior to drug use. Sperm concentrations were unchanged in both placebo and nizatidine exposed men, but were significantly reduced (p less than 0.05) in the cimetidine exposed men. Based on these data, nizatidine does not appear to influence hormone function or fertility.

Effects of corticotropin releasing factor and growth hormone releasing factor on pituitary hormone secretion in patients with congenital thyrotropin deficiency. Abnormal response of growth hormone to corticotropin releasing factor

Blood concentrations of anterior pituitary hormones, ACTH, GH, TSH, PRL, LH, and FSH were determined in corticotropin releasing factor (CRF) test (synthetic ovine CRF 1.0 microgram per kg body weight) and growth hormone releasing factor (GRF) test (synthetic human pancreatic GRF-44 100 micrograms) in 2 female sibling patients with congenital isolated TSH deficiency, in their mother, in 2 patients with congenital primary hypothyroidism and in 8 normal controls. The patients with isolated TSH deficiency showed normally increased plasma ACTH and serum GH after CRF and GRF, respectively, and also showed an abnormal GH response to CRF. The serum GH showed a rapid increase to maximum levels (12.9 ng/ml) within 30 to 60 min followed by decrease. The possibility of secretion of abnormal GH could be excluded by the fact that on serum dilution, GH value gave a linear plot passing through zero. In addition, serum PRL, LH and FSH levels after CRF administration in case 1 and PRL after GRF in case 2 were also slightly increased but these responses were marginal. The mother of the patients, patients with congenital primary hypothyroidism, and normal healthy controls showed normal responses of pituitary hormones throughout the experiment. Data from the present study and a previous report show that abnormal GH response to the hypothalamic hormones (CRF, TRH and LHRH) may be observed in patients with congenital isolated TSH deficiency.

Effects of intake and postruminal casein infusion on performance and concentrations of hormones in plasma of lactating cows

Four Holstein cows were utilized in a Latin square design with a factorial arrangement of treatments to examine the interaction between effects of dry matter intake (107 vs. 78% of energy requirements) and postruminal infusions (water vs. 395 g/d casein) on lactational performance, utilization of nitrogen and energy, and plasma concentrations of hormones. Yields of milk and milk protein were decreased by feed restriction and increased by casein infusion with no treatment interactions. Restricting feed intake decreased total nitrogen intake by 143 g/d and resulted in smaller quantities of fecal, absorbed, urinary, milk, and retained nitrogen compared with cows fed ad libitum. Casein infusion increased total nitrogen intake (55 g/d), absorbed nitrogen (54 g/d), urinary nitrogen excretion (28 g/d), and milk nitrogen (13 g/d). Casein by dry matter intake interactions were not significant for nitrogen utilization. Restricting feed intake increased plasma growth hormone and decreased concentrations of insulin and triiodothyronine. Glucagon, prolactin, and thyroxine were not affected by intake. Casein infusion did not affect growth hormone, insulin, prolactin, triiodothyronine, or thyroxine. Increased milk and milk protein yields obtained with casein infusion were apparently not mediated through changes in circulating concentrations of these hormones; however, plasma glucagon was increased by casein infusions.

Stimulation of the circulating levels of glycoprotein hormone alpha-subunit after combined administration of a luteinizing hormone-releasing hormone (LHRH) agonist and flutamide in patients with cancer of the prostate

To ascertain whether the immunoreactive luteinizing hormone (LH) levels measured following the combined treatment may represent cross-reaction of the LH antiserum with LH subunits, we have examined the effects of therapy on the serum levels of free alpha- and free LH-beta-subunits in intact, castrated, and estrogen-treated patients. In previously untreated patients receiving the LHRH agonist [D-Trp6,des-Gly-NH2(10)]LHRH ethylamide in association with the pure antiandrogen Flutamide, serum-free alpha-subunit levels were stimulated from 0.09 +/- 0.02 to 3.10 +/- 0.84 ng/ml after 5 days, and declined slowly afterwards to 1.33 +/- 0.20 ng/ml after 3 months of combined treatment. In patients pretreated from 12 to 24 months (17.5 +/- 1.0 months) with diethylstilbestrol (DES) prior to receiving the combined therapy, free serum alpha-subunit concentration followed a similar pattern, rising from 0.22 +/- 0.03 to 1.78 +/- 0.28 ng/ml after 15 days of combined treatment, and declining thereafter to 0.81 +/- 0.10 ng/ml after 3 months. Free LH-beta-subunits were below the detection limit in most previously untreated patients and in all DES-treated patients. After correcting for the cross-reactivity of the alpha-subunit in the LH RIA, immunoassayable LH serum levels in previously untreated patients were only slightly reduced from 0.81 +/- 0.06 ng/ml before the onset of the combined treatment to 0.52 +/- 0.05 ng/ml after 3 months. On the contrary, bioactive serum LH levels were drastically inhibited from 0.43 +/- 0.04 to 0.03 +/- 0.01 ng/ml after the same duration of treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Endocrine effects of repeated sauna bathing

Ten healthy male and seven female volunteers were exposed to dry heat (in a Finnish sauna 80 degrees C) 1 h twice a day for 7 days. The levels of ACTH in plasma, cortisol, TSH, thyroid hormones, testosterone, gonadotropins, prolactin and GH in serum and urinary excretion of catecholamines were determined before the experiment, and on the first, third and seventh days. Females participated only in prolactin studies. During the experiments there were no statistically significant changes in serum thyroid hormones, TSH, testosterone, FSH and LH levels. Serum cortisol and plasma ACTH decreased and urinary catecholamine increased slightly at the end of the experiment (P less than 0.05). Serum GH and prolactin in males exhibited 16- and 2.3-fold increases (P less than 0.01), respectively. In females serum prolactin rose over four-fold (P less than 0.01). The GH rise in response to hyperthermia declined after the third day but prolactin remained elevated at the end of the experiments in males. The release of prolactin in females was also high and may be associated with the transient amenorrhoea that occurred in five out of seven subjects after the experiment. The increased release of prolactin and perhaps that of GH may be associated to the heat-exposure-induced dehydration.

Sellar lesions associated with isolated hyperprolactinaemia. Morphological, immunocytochemical, hormonal and clinical results

In 204 patients with sellar lesions and isolated hyperprolactinaemia we analysed and compared many different morphological, immunocytochemical, hormonal, and clinical data for a differentiation of primary (Prl produced by a tumour) and secondary (Prl elevation by PIF inhibition) hyperprolactinaemia. We found Prl-positive pituitary adenomas with primary hyperprolactinaemia in 62.7% and a secondary Prl elevation with different alterations in 37.3% (Prl-negative adenomas 28.9%, craniopharyngeomas 5%, and non-tumourous conditions 3.4%). In secondary hyperprolactinaemia the Prl values did not exceed 130 micrograms/l, higher levels indicated Prl-producing adenomas with a high probability. In patients with Prl elevation below 130 micrograms/l the clinical and sometimes the morphological analysis were not sufficient for a differentiation. Here immunocytochemical studies are necessary for a clear classification of hyperprolactinaemia.

Neuroendocrine effects of the dopamine agonist piribedil in depressed patients

Piribedil is a relatively selective dopamine agonist with moderate antidepressant activity. Although of limited clinical use, piribedil may elucidate the mechanism of the neuroendocrine effects of treatments useful in manic-depressive illness, particularly those involving the thyroid axis. Therefore, the effect of chronic piribedil treatment on peripheral thyroid hormones, as well as the pituitary hormone responses to sequential stimuli, namely arginine, thyrotropin-releasing hormone (TRH), and luteinizing hormone releasing hormone, were studied in patients with major depression. The drug was found to decrease peripheral thyroid hormones and the thyroid stimulating hormone response to TRH, but it did not affect prolactin, growth hormone, or the gonadotropins. The advantages of the experimental design and the implication of these findings for dopaminergic mechanisms in both the regulation of pituitary hormones and the treatment response of affective illness are discussed.

Dynorphin effects on plasma concentrations of anterior pituitary hormones in the nonhuman primate

The role of dynorphin-(1-13) and dynorphin-(1-10)-amide in the neuroendocrine control of primate anterior pituitary hormones was studied in nonrestrained, ovariectomized rhesus monkeys. The effects of these opioids on plasma concentrations of prolactin (PRL), luteinizing hormone (LH), follicle stimulating hormone (FSH) and thyrotropin (TSH), and interactions with naloxone are reported here. Intravenous administration of dynorphin-(1-13), 30 to 120 micrograms/kg, significantly increased plasma PRL levels 3- to 4-fold. These PRL increases occurred within 5 min and levels remained elevated for at least 60 min. Administration of naloxone (1.0 mg/kg i.v.) antagonized the rise in PRL levels. Dynorphin-(1-13) had no significant effect on plasma LH, FSH or TSH levels. Dynorphin-(1-10)-amide (30-120 micrograms/kg) increased plasma PRL levels 2- to 4-fold at 5 to 40 min after administration. Plasma LH levels were significantly depressed 100 to 120 min postdrug. Dynorphin-(1-10)-amide produced no change in plasma FSH or TSH levels. These results indicate that dynorphin is involved in the modulation of PRL and perhaps LH secretion, although not affecting TSH or FSH release.

Concentrations of prolactin, luteinizing hormone and follicle stimulating hormone in pituitary and serum of horses: effect of sex, season and reproductive state

Pituitary and serum from 86 male or female horses of various reproductive states were collected in the normal breeding season (summer) and in the nonbreeding season (winter) at a commercial slaughterhouse. Concentrations of prolactin (PRL), luteinizing hormone (LH) and follicle stimulating hormone (FSH) were measured by radioimmunoassay. Concentrations of pregnant mare serum gonadotropin and reproductive steroids in serum and gross appearance of the reproductive tract and gonads were used to catagorize reproductive state. Concentrations of PRL were higher (P less than .01) in summer than in winter in pituitary and serum of mares, stallions and geldings. In summer, mares had higher (P less than .01) concentrations of PRL in serum than stallions. In mares, concentrations of LH in pituitary were higher (P less than .05) in summer than in winter. Concentrations of LH in serum were higher (P less than .01) in summer than in winter in mares and geldings, higher (P less than .01) in mares than in stallions in summer, higher (P less than .01) in geldings than in stallions in summer and higher (P less than .01) in mares with low serum progesterone (P) concentrations than in mares with high P concentrations in summer. Concentrations of FSH in pituitary and serum did not differ between summer and winter for any type of horse.(ABSTRACT TRUNCATED AT 250 WORDS)

Response of anterior pituitary hormones to chronic stress. The specificity of adaptation

The effect of chronic noise stress on the response of anterior pituitary hormones to the same or to another stressor (forced swimming) was studied in adult male Wistar rats. Both acute stressors increased corticosterone, prolactin, LH and TSH secretion and inhibited GH secretion. Previous chronic exposure to noise reduced corticosterone response to the same stimulus without modifying corticosterone response to a novel acute stress. Neither prolactin nor TSH responses to acute noise were reduced by previous chronic exposure to noise. Since chronic noise increased basal levels of LH and decreased those of GH, the response of these hormones to acute stress was expressed as percent changes of their respective basal values. It was found that chronically stressed rats showed diminished LH response to noise but not to forced swimming. GH showed the same pattern without reaching statistical significance. These data indicate that the response of some anterior pituitary hormones can adapt after repeated exposure to the same stressor. When adaptation occurred, this was specific for the stressor which the animals were repeatedly exposed to. The pituitary-adrenal axis appears to be the most reliable index of adaptation to chronic stress among all the anterior pituitary endocrine axes.

The significance of alpha-subunit as a tumor marker for gonadotropin-producing pituitary adenomas

We studied gonadotropin hormone alpha-subunit and gonadotropin secretion in four patients with gonadotropin-producing pituitary adenomas. All four patients had elevated plasma alpha-subunit levels, ranging from 2.8-8.5 ng/ml (normal, less than 0.5 ng/ml). alpha-Subunit responses to LHRH were less than those in seven patients with primary gonadal failure. The relative proportions of the gonadotropin and alpha-subunit peaks in one patient were the same before and after LHRH administration, based on gel filtration studies of plasma. The alpha-subunit levels decreased little during testosterone treatment in the two adenoma patients so treated. Immunohistochemical study of the adenomas from two patients demonstrated definite staining with alpha-subunit and gonadotropin antisera. Elevated plasma levels of alpha-subunit and its relative unresponsiveness to LHRH stimulation or testosterone suppression suggest that the alpha-subunit originated in tumor tissue and that its measurement is useful for the diagnosis of a gonadotropin-producing tumor in patients with elevated plasma levels of LH and/or FSH.

Influence of yohimbine on release of anterior pituitary hormones

We used a double-blind crossover design to study the effects of alpha 2 adrenoreceptor blockade with yohimbine on levels of anterior pituitary hormones. A dose of yohimbine was used which raised plasma norepinephrine from 379 +/- 74 (S.E.) to 730 +/- 143 pg/ml and mean arterial pressure from 83 +/- 4 to 92 +/- 5 torr (p less than 0.025). This dose (125 micrograms/kg, then 1 microgram/kg/min) also altered mood when compared to saline infusion. In spite of these changes, when prolactin, cortisol, ACTH, beta-endorphin, TSH and growth hormone were measured after 45 minutes of yohimbine infusion, no changes from baseline were noted. These data suggest that in normal man, at rest, alpha 2 adrenoreceptors in the hypothalamus, adenohypophysis or other brain areas do not tonically modulate release of these hormones into the blood.

Abnormal beta-endorphin and beta-lipotropin responses to TRH and LRH administration in primary and secondary affective disorders

Anomalous anterior pituitary hormone responses to acute administration of TRH and LRH have previously been observed in patients with primary affective disorders (PAD), with TRH eliciting GH, FSH and LH rises, and LRH eliciting GH and Prl rises. We examined whether the same unusual responses were present also for beta-endorphin (beta-EP) and beta-lipotropin (beta-LPH) in 15 PAD patients, in 9 patients with secondary affective disorders (SAD), and in 7 controls. TRH (500 micrograms iv) elicited rises of beta-EP plasma levels in 5 PAD and 2 SAD patients, and of beta-LPH in 4 PAD and 3 SAD patients. LRH (150 micrograms iv) elicited rises of plasma beta-EP levels in 2 PAD and 2 SAD patients, and of beta-LPH in 5 PAD and 2 SAD patients. No rises of beta-EP and beta-LPH plasma levels were observed in PAD patients after saline administration, nor in the controls after TRH, LRH or saline administration.

Endocrine impact of pure estradiol replacement in postmenopausal women: alterations in anterior pituitary hormone release and circulating sex steroid hormone concentrations

Thirteen healthy postmenopausal volunteers were studied under basal conditions and at intervals (days 1, 5, 10, and 30) after intravaginal placement of a polysiloxane ring impregnated with 400 mg of estradiol. Mean serum estradiol concentrations rose 26-fold with a twofold increase in serum estrone concentrations. Serum delta 4-androstenedione, dehydroepiandrosterone sulfate, and total testosterone did not change, but absolute and percent free testosterone concentrations declined significantly by day 5. Concurrently, serum concentrations of immunoactive follicle-stimulating hormone declined progressively, while serum luteinizing hormone and free alpha-subunit concentrations exhibited a biphasic pattern of suppression. Serum levels of prolactin increased monophasically and those of growth hormone, somatomedin C, and thyroid-stimulating hormone did not change.

Plasma immunoreactive proopiomelanocortin peptides and cortisol in normal dogs and dogs with Addison's disease and Cushing's syndrome: basal concentrations

We measured basal plasma concentrations of the immunoreactive (IR) proopiomelanocortin (POMC)-derived peptides ACTH, beta-lipotropin (beta LPH), beta-endorphin (beta END), and alpha MSH in 160 normal dogs, 32 dogs with Addison's disease, 42 dogs with adrenocortical tumors causing Cushing's syndrome, and 169 dogs with pituitary-dependent Cushing's disease. In normal dogs, plasma IR-POMC peptide levels were similar to those in man, except that IR-alpha MSH, a pars intermedia POMC product, was readily detected. In Addisonian dogs, plasma cortisol was decreased, and the IR-POMC peptides were increased, except for IR-alpha MSH, which was normal. In 7 Addisonian dogs given dexamethasone, elevated plasma IR-ACTH, beta LPH, and beta END levels fell dramatically. In dogs with Cushing's syndrome due to adrenal tumors, plasma IR-ACTH, beta LPH, and beta END were decreased, and cortisol was increased, but IR-alpha MSH was normal. Dogs with Cushing's disease due to pars distalis tumors had elevated plasma IR-ACTH, beta LPH, beta END, and cortisol, but normal IR-alpha MSH; their plasma cortisol was suppressed by dexamethasone. There appeared to be 2 types of pars intermedia tumors causing Cushing's disease: 1 dexamethasone nonsuppressible and with disproportionately high plasma IR-alpha MSH levels, the other relatively dexamethasone suppressible and with normal to slightly elevated IR-alpha MSH levels. These 2 pars intermedia tumor types may arise from 2 distinct normal canine pars intermedia cell types. Canine Cushing's disease may provide a useful model for variants of the disorder in man.

Luteinizing hormone (LH) and prolactin-releasing pituitary tumor: possible malignant transformation of the LH cell line

A pituitary tumor was diagnosed in a prepubertal 13-yr-old girl, who had elevated plasma LH (58 mIU/ml) and PRL (93 ng/ml) levels; decreased GH, ACTH, and FSH secretion; and diabetes insipidus. After surgery, plasma LH and PRL declined, but not to normal levels. Conventional external radiotherapy to the pituitary was immediately followed by a decrease in LH to prepubertal values (0.7 mIU/ml), while PRL levels became normal only after a long course of bromocriptine therapy. The pituitary tumor was composed of two distinct cell types: small polygonal cells, which were PRL positive by immunohistochemistry, and clusters of pleomorphic large frequently mitotic polynucleated cells, which were LH positive, some of them also being positive for the alpha-subunit or beta LH but not for beta FSH. Four years after surgery and radiotherapy, the patient deteriorated neurologically. Computed tomographic scan showed widespread frontal and periventricular tumor, which had the histological features of a poorly differentiated carcinoma. No PRL, LH, or alpha- or beta-subunits were detectable on immunocytochemistry. While the PRL-positive cells of the pituitary tumor displayed the histological and clinical features of PRL adenomas, the morphological characteristics of LH cells and the sharp decline of plasma LH levels after radiotherapy were suggestive of malignant transformation. In this context, the later brain tumor could have been the result of subependymal spread of the pituitary tumor after it lost its hormone-secreting capacity.

Persistent effects of a marathon run on the pituitary-testicular axis

Plasma levels of testosterone (T), LH, FSH, prolactin (PRL), cortisol (F), dehydroepiandrosterone sulfate (DHAS), noradrenaline (NA), NA sulfate (NAS), adrenaline (A) and A sulfate (AS) were measured in 7 adult males before and immediately after a marathon run as well as every morning for 5 days after the run. While plasma T levels fell significantly on the first and the second postmarathon day, those of LH rose significantly during the first 3 postrun days. Plasma PRL and F values increased significantly only at the end of the marathon. Plasma levels of NA and NAS rose significantly at the end of the run and again on days 2 and 5 postmarathon, respectively. A similar pattern was observed for A and AS except for the second peak of free A. These results show that a strenuous physical exercise leads to a persistent relative insensitivity to LH of the testicular T biosynthetic machinery, while the feedback mechanisms operating at the hypothalamic-pituitary level are normal. Furthermore, they suggest that catecholamines may be responsible for the prolonged inhibitory effect of stress on T biosynthesis.

Hormonal and metabolic effects following a football match

Hormonal and metabolic parameters were studied for two teams after a football match. Blood samples were collected before the start, at half-time, at the end, and 45 and 90 min after the end of the game. In the first team, ACTH, cortisol, and lactate levels increased significantly during the whole match to resume basal levels in the fourth sample (45 min after the end of play). HGH, prolactin, and blood glucose were found to be increased only at half-time. The second team had an intense and long warm-up period before the match and the lactate concentrations were already elevated in the first sample. All the other parameters, except ACTH and glucose, displayed a pattern similar to that of the first team. The differences in the time courses of the hormonal and metabolic values are discussed.

Central and peripheral cholinesterase inhibition: effects on anterior pituitary and sympathomimetic function

Ten physically healthy inpatients of mixed diagnosis received, in a randomized, counterbalanced double-blind paradigm, physostigmine (22 micrograms/kg) and neostigmine (11 micrograms/kg). Infusions were separated by at least 2 days. The differential effects of physostigmine and neostigmine on plasma concentrations of cortisol, prolactin, growth hormone, ACTH, beta-endorphin/beta-lipotropin-like immunoreactivity, dopamine, norepinephrine, and epinephrine are reported. Administration of physostigmine, unlike that of neostigmine, was associated with statistically significant increases in plasma concentrations of cortisol, prolactin, ACTH, beta-endorphin/beta-lipotropin-like immunoreactivity, and epinephrine, presumably via central mechanisms. In a separate study, 15 subjects, mostly depressed inpatients, were pretreated with methscopolamine (0.75 mg) on one day and scopolamine (0.5 mg) on another day, at least 2 days apart, in a randomized, counterbalanced double blind paradigm and subsequently on each day received physostigmine (22 micrograms/kg). Scopolamine significantly attenuated the physostigmine-associated increase in plasma concentrations of cortisol, growth hormone, prolactin, ACTH, and dopamine compared to methscopolamine, and a close-to-significant attenuation of epinephrine as well. These results provide further evidence that physostigmine's effects on plasma concentrations of pituitary hormones and epinephrine occur via central mechanisms and are muscarinically mediated.

Administration of low dose pulsatile gonadotropin-releasing hormone (GnRH) to GnRH-deficient men regulates free alpha-subunit secretion

Although pharmacological doses of GnRH and TRH stimulate free alpha-subunit (alpha-subunit) secretion from the pituitary, little is known about the pattern and control of alpha-subunit release under physiological circumstances. Euthyroid men with idiopathic hypogonadotropic hypogonadism, a condition of deficient GnRH release, provide a unique opportunity to study alpha-subunit secretion before and during administration of a physiological regimen of GnRH administration. Before GnRH therapy, six euthyroid IHH men with normal endogenous TSH secretion had circulating alpha-subunit levels close to or below assay detection limits, with a mean level less than 0.5 ng/ml. During 12-42 weeks of physiological GnRH replacement, serum alpha-subunit concentrations rose to a mean value of 2.07 +/- 0.3 (+/- SEM) ng/ml (P less than 0.01). After GnRH administration, alpha-subunit was released in a pulsatile pattern following each dose of GnRH and mirrored the secretory pattern of LH. Increases in serum alpha-subunit concentrations during GnRH administration were closely correlated with increases in LH (r = 0.91; P less than 0.01), but not FSH (r = 0.24; P = NS), levels. In addition, a situation in which LH secretion was clearly predominant and FSH levels were barely detectable was created by increasing the frequency of GnRH administration to every 30 min. In this circumstance, free alpha-subunit concentrations increased in conjunction with LH levels in the face of decreased FSH levels. We conclude that replacement of GnRH regulates both the level and pattern of alpha-subunit secretion in GnRH-deficient men, and that there is tight correlation of alpha-subunit with LH, but not with FSH, secretion.

Anterior pituitary hormone responses to a kappa-opioid agonist in man

The present study was designed to investigate pituitary hormone responses to a kappa-opiate receptor agonist in man. Normal men were given the racemic benzomorphan kappa-agonist MR 2033 or its levorotatory isomer MR 2034 iv. Plasma levels of PRL and GH markedly increased after injection of 3.5 micrograms/kg MR 2033 or 1.9 or 3.8 micrograms/kg MR 2034. These effects of MR 2033 were blocked by the opiate antagonist naloxone (10 mg), thereby demonstrating their mediation by opiate receptors. The kappa-agonist did not change plasma levels of LH and FSH. The secretion of TSH was significantly suppressed by MR 2033 and MR 2034, but this action was not antagonized by pretreatment with naloxone. The suppression of plasma TSH was, however, stereospecific since the (+)-isomer, MR 2035, did not affect TSH secretion. These data indicate that kappa-opiate receptors are located on neuronal pathways regulating GH, TSH, and PRL secretion. The pattern of pituitary responses elicited by the kappa-agonist differs from that of mu-opioid agonists, indicating differential endocrine functions for the endogenous agonists.