Influence of endogenous opiates on anterior pituitary function

In general, the endogenous opioid peptides (EOP), morphine (MOR), and related drugs exert similar effects on acute release of pituitary hormones. Thus administration of opiates produces a rapid increase in release of prolactin (PRL), growth hormone (GH), adrenocorticotropin (ACTH), and antidiuretic hormone (ADH), and a decrease in release of gonadotropins and thyrotropin (TSH). Although not yet fully established, there is growing evidence that the EOP participate in the physiological regulation of pituitary hormone secretion. Thus naloxone (NAL), a specific opiate antagonist, has been shown to reduce basal serum levels of PRL and GH, and to elevate serum levels of LH and follicle stimulating hormone in male rats. Other reports have shown that NAL can inhibit the stress-induced rise in serum PRL, raise the castration-induced increase in serum LH to greater than normal castrate values, and counteract the inhibitory effects of estrogen and testosterone on LH secretion. Opiates appear to have no direct action on the pituitary, but there is evidence that they can alter activity of hypothalamic dopamine and serotonin in modulating secretion of pituitary hormones.     

Effects of naloxone,morphine and methionine enkephalin on serum prolactin,luteinizing hormone,follicle stimulating hormone,thyroid stimulating hormone and growth hormone

The response of 5 anterior pituitary hormones to single injections of naloxone, morphine and metenkephalin administration was measured in male rats. Morphine and met-enkephalin significantly increased serum prolactin and GH concentrations, and significantly decreased serum LH and TSH concentrations. Naloxone reduced serum prolactin and GH concentrations, increased serum LH and FSH, but had little effect on serum TSH concentrations. Concurrent injections of naloxone with morphine or met-enkephalin reduced the response to each of the drugs given separtely. These results suggest that endogenous morphinomimetic substances may participate in regulating secretion of anterior pituitary hormones.     

The involvement of cyclic-3',5'-AMP in the release of hormones from the anterior pituitary in vitro.

DBcAMP significantly increased the release of GH but not of LH, FSH, TSH, or PRL, except in the presence of hypothalamic extract when it augmented the release of LH, FSH, and GH, reversed the inhibition of PRL, but did not further influence TSH release. Theophylline increased release of GH and PRL while inducing increased tissue content of cAMP without consistently increasing the release of TSH, LH, or FSH. Hypothalamic extractor K+-stimulated hormone rel-ase was consistently and significantly potentiated by theophylline. Neither hypothalamic extract, increased [K+], or synthetic TRH and LRH were able to raise tissue content of cAMP while producing their expected effects on hormone release. Cholera enterotoxin produced a highly significant increase in tissue content of the cyclic nucleotide but increased the release of GH only, and not that of LH, FSH, TSH, or PRL. DBcAMP was able to lower the threshold concentration of K+ required to stimulate release of GH, LH, and FSH and also to augment K+-stimulated release to the higher levels induced by the hypothalamic releasing hormones. It did not augment K+-induced release of TSH.     

Spontaneous recovery from hypopituitarism due to postpartum hemorrhage

A rare case is presented of a woman with spontaneous recovery from hypopituitarism following postpartum hemorrhage. One month after delivery, serum thyroid hormone, TSH, LH and FSH levels were low, and their secretion from the pituitary gland responded poorly to the TRH and LH-RH tests. Pituitary TSH response was normal 3 months after delivery. In the LH-RH test, pituitary LH and FSH response returned to normal at 2 months. Pituitary GH secretion and serum cortisol levels induced by ITT already responded normally one month postpartum. Excessive secretion of pituitary PRL was observed 3 months after delivery and improved gradually thereafter. These results indicate that the secretion of pituitary tropic hormones was sensitive to pituitary ischemia in the following order: TSH, gonadotropin, GH and ACTH. The disturbance of these hormones also persisted in the same order.     

Inhibitory effects of cysteamine on neuroendocrine function

The action of cysteamine on anterior pituitary hormone secretion was studied in vivo using conscious, freely moving male rats and in vitro using anterior pituitary cells in monolayer culture. Administration of 500 micrograms cysteamine into the lateral cerebral ventricles of normal rats caused the complete inhibition of pulsatile GH secretion for a minimum of 6 h. This treatment also significantly decreased plasma concentrations of LH for at least 6 h in orchiectomized rat, TSH in short-term (0.5 month) thyroidectomized rats, and PRL in long-term (6 months) thyroidectomized rats. The in vivo stimulation of GH, LH, TSH and PRL with their respective releasing hormones 60 min after administration of cysteamine was not different from the response observed in rats pretreated with saline except for PRL where cysteamine pretreatment significantly inhibited the expected PRL increase. In vitro, 1 mM cysteamine decreased basal and TRH stimulated PRL release while not affecting basal or stimulated GH, LH, TSH and ACTH secretion. These data demonstrate the dramatic and wide-ranging effects of cysteamine on anterior pituitary hormone secretion. This action appears to be mediated through hypothalamic pathways for GH, LH and TSH and through a pituitary pathway for PRL.     

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.     

Gonadal steroids and neuropeptide Y-opioid-LHRH axis: interactions and diversities

We report that the two classes of regulatory neuropeptides, neuropeptide Y (NPY) and endogenous opioid peptides (EOP), modulate luteinizing hormone (LH) release in diverse fashion in gonad-intact rats. Each neuropeptide acts at two loci, the hypothalamus and pituitary, to excite (NPY) or inhibit (EOP) LH release. At the hypothalamic level, NPY stimulates luteinizing hormone releasing hormone (LHRH) release, a response mediated by alpha 2-adrenoreceptors and amplified in the presence of adrenergic agonists. At the pituitary level, NPY acts in concert with LHRH to amplify the LH response. In contrast, EOP inhibit LHRH release by decreasing the supply of excitatory adrenergic signals in the vicinity of LHRH neurons in the preoptic-tuberal pathway, and at the pituitary level, they decrease LH release in response to LHRH. Further, the gonadal steroidal milieu facilitates NPY neurosecretion and postsynaptic expression of NPY in concert with adrenergic system; a similar clear-cut facilitatory effect of gonadal steroids on EOP secretion is not yet obvious. Our additional studies imply that the EOP system has the potential to increase sensitivity towards gonadal steroids and that to induce the preovulatory LH surge the neural clock may decrease the inhibitory EOP tone prior to the critical period on proestrus. This antecedent neural event allows the excitatory adrenergic and NPY signals to evoke LHRH secretion at a higher frequency approximating that seen in ovariectomized rats. Further studies are under way to delineate the steroid-induced subcellular events that integrate the action of these regulatory peptides in the control of the episodic LHRH secretion pattern which sustains basal and cyclic gonadotropin release in the rat.     

Effects of hypothalamic-releasing hormones on LH, FSH, and prolactin in pituitary monolayer cultures.

Four-day-old pituitary monolayer cultures were incubated with various hypothalamic releasing hormones. Rat hypothalamic extract stimulated the release of LH, FSH, and PRL by these cultures in a dose-related fashion. Synthetic LH-RH stimulated the release of LH and FSH but not of PRL. Synthetic TRH increased the release of PRL but had no effect on LH or FSH. At 10(-8) M, somatostatin did not affect any of the three adenohypophyseal hormones. Incubation with DBcAMP or theophylline also stimulated PRL release without any detectable effect on LH and FSH release. These data suggest the involvement of cyclic AMP--adenylate cyclase system in the mechanism of PRL release, but their involvement in gonadotropin release requires further studies.     

Participation of voltage-sensitive calcium channels in pituitary hormone release

The role of extracellular Ca2+ in pituitary hormone release was studied in primary cultures of rat anterior pituitary cells. The basal levels of luteinizing hormone (LH), follicle-stimulating hormone (FSH), thyrotropin (TSH), and adrenocorticotropin (ACTH) secretion were independent of extracellular Ca2+ concentration ([Ca2+]e). In contrast, the basal levels of growth hormone (GH) and prolactin (PRL) release showed dose-dependent increases with elevation of [Ca2+]e, and were abolished by Ca2+-channel antagonists. Under Ca2+-deficient conditions, BaCl2 mimicked the effects of calcium on PRL and GH release but with a marked increase in potency, and also increased basal LH and FSH release in a dose-dependent manner. In the presence of normal [Ca2+]e, depolarization with K+ maximally increased cytosolic [Ca2+] ([Ca2+]i) from 100 to 185 nM and elevated LH, FSH, TSH, ACTH, PRL, and GH release by 7-, 5-, 4-, 3-, 2-, and 1.5-fold, respectively. These effects of KCl were abolished in Ca2+-deficient medium or in the presence of the Ca2+-channel antagonist, Co2+, and were diminished by the dihydropyridine Ca2+-channel antagonist, nifedipine. The Ca2+-channel agonist BK 8644 (100 nM) enhanced the hormone-releasing actions of 25 mM KCl upon PRL, LH, FSH, GH, TSH, and ACTH by 2.3-, 2.0-, 1.8-, 1.7-, 1.6-, and 1.4-fold, respectively. The dose- and voltage-dependent actions of BK 8644 were specific for individual cell types; BK 8644 enhanced GH, PRL, TSH, LH, and ACTH secretion in the absence of any depolarizing stimulus, with ED50 values of 8, 10, 150, 200, and 400 nM, respectively. However, in the presence of 50 mM KCl, the ED50 values for BK 8644 were 1.5, 2, 3, 5, and 7 nM for GH, PRL, ACTH, TSH, and LH, respectively. [3H]BK 8644 bound specifically to pituitary membranes with Kd values of 0.8 nM and concentrations of about 900 channels per cell. These observations provide evidence for the presence and participation of voltage-sensitive calcium channels in the secretion of all five populations of anterior pituitary cells.     

Monolayer cultures of dispersed cells from bovine anterior pituitary: responses to synthetic hypophysiotropic peptides.

Cells were dispersed from bovine anterior pituitary glands, by digestion with collagenase, and cultured. After 4 days the cell monolayers were incubated with fresh medium containing synthetic hypophysiotropic peptides for 2, 6, or 20 h, and hormone released into the medium was estimated by radioimmunoassay. After 2 h, thyroid releasing hormone (TRH) stimulated the release of thyroid-stimulating hormone (TSH) up to eightfold, and of prolactin (PRL) and follicle-stimulating hormone (FSH) about twofold at a minimal effective concentration of 1 ng/ml; enhanced growth hormone (GH) release was not apparent until 20 h, and release of luteinizing hormone (LH) and adrenocorticotrophic hormone (ACTH) was unaffected. Luteinizing hormone releasing hormone (LH-RH) enhanced release of LH maximally (three- to fourfold) during a 2 h incubation and was effective at 0.1 ng/ml; FSH release was significantly enhanced by about 50% above control level. Growth hormone release inhibiting hormone (GH-RIH)(somatostatin) showed significant effects only in the 20 h incubation; GH release was inhibited by 50% and release of PRL was slightly, but significantly, enhanced. Pituitary cell monolayers apparently permit maximal expression of releasing activities inherent in the hypothalamic hormones.     

Evaluation of hypothalamic-pituitary function in a combination of tests with four hypothalamic releasing hormones and L-dopa in normal subjects and in patients with hypothalamic and/or pituitary disorders

Hypothalamic-pituitary function was evaluated in a combination of tests with four hypothalamic releasing hormones (4RHs) and L-dopa in normal subjects and in patients with hypothalamic and/or pituitary disorders. Plasma concentrations of anterior pituitary hormones (GH, ACTH, TSH, PRL, LH and FSH) were measured before and after simultaneous iv administration of GHRH, CRH, TRH and LHRH. In addition, changes in the plasma levels of GHRH and GH were investigated before and after oral administration of L-dopa. Normal subjects showed appreciable responses to both tests. In five patients with hypothalamic disorders, the response of plasma anterior pituitary hormones varied, but plasma GHRH and GH did not respond to L-dopa. Patients with idiopathic and postpartum hypopituitarism showed low response to 4RHs or none at all, but L-dopa evoked a normal GHRH response in 2 of the 4 cases having no GH response. In the patients with hypopituitarism due to resection of a pituitary tumor, the response of anterior pituitary hormones to 4RHs was low, and L-dopa administration induced a normal GHRH and low GH response in 5 out of the 7 cases. After 4RHs administration, the patients with ACTH deficiency syndrome showed different patterns of impaired ACTH secretion, and isolated, combined or limited ACTH reserve. Seven patients with anorexia nervosa showed exaggerated GH, delayed TSH and FSH, low ACTH and LH, that is, normal PRL response to 4RHs, but no response of plasma GHRH or GH to L-dopa, suggesting the presence of hypothalamic dysfunction. These results indicate that the combination of the 4RHs test and L-dopa test is a simple and useful means for evaluating hypothalamic-pituitary function by measuring the response of plasma GHRH and six anterior pituitary hormones in the patients with endocrine disorders.     

Growth hormone and prolactin secretion after hypothalamic deafferentation in pigs

Control of growth hormone (GH) and prolactin (PRL) secretion was investigated in ovariectomized, prepuberal Yorkshire gilts by comparing the effects of anterior (AHD), complete (CHD), and posterior (PHD) hypothalamic deafferentation with sham-operated controls (SOC). Blood samples were collected sequentially via an indwelling jugular catheter at 20-min intervals during surgery and recovery from anesthesia (Day 0) and Days 1 and 2 after cranial surgery. Mean serum concentrations of GH after AHD, CHD, and PHD were reduced (P less than 0.01) when compared with SOC gilts. Furthermore, episodic GH release evident in SOC animals was obliterated after hypothalamic deafferentation. PRL concentrations in peripheral serum of hypothalamic deafferentated gilts remained similar (P greater than 0.05) to those of SOC animals. These results indicate that anterior and posterior hypothalamic neural pathways play a minor role in the control of PRL secretion in the pig in as much as PRL levels remained unchanged after hypothalamic deafferentation. These findings may be interpreted to suggest that the hypothalamus by itself seems able to maintain tonic inhibition of PRL release. In contrast, the maintenance of episodic GH secretion depends upon its neural connections traversing the anterior and posterior aspects of the hypothalamus in the pig.     

Effects of morphine and naloxone on serum LH, FSH and prolactin levels and on hypothalamic content of LH-RF in proestrous rats.

Proestrus surges of serum LH, FSH and prolactin (PRL) were significantly reduced when morphine HCl (50 and 10 mg/kg) was administered to 4-day cycling rats just prior to the proestrous critical period. The inhibitory effect of morphine was reversed by naloxone, a morphine antagonist, at the dose which had no effect on the proestrus surges of serum LH, FSH or PRL. The hypothalamic LH-RF content of proestrous rats at 1800 hr (during the proestrus surge) was not significantly different from that at 1400 hr (before the surge) and was not affected by pretreatment with morphine or naloxone. Our results suggest that naloxone reverses the anti-ovulatory effect of morphine by antagonizing the inhibitory effect of morphine on preovulatory surges of gonadotropins or PRL.     

Effect of prolonged incubation of male rat whole pituitary or pituitary-hypothalamus complex with testosterone on release of gonadotrophin and prolactin in vitro.

Investigations were undertaken to study the effect of in vitro addition of testosterone (0.3 mM) on the release of luteinizing hormone (LH), follicle stimulating hormone (FSH) and prolactin (PRL) by pituitary-hypothalamus complex (PHC) or the whole pituitary (PI) incubated for 72 hr, with incubation media changed every 24 hr. PHC or PI were from adult intact or castrated (7 days post castration) rats. The tissues incubated with or without testosterone were further exposed to 0.1 nM luteinizing hormone-releasing hormone (LHRH) for 4 hr. Incubation media and the pituitary were analyzed for PRL and gonadotrophin content. While PHC from normal and castrated rats released increasing amounts of LH with diminishing amounts of FSH and PRL at different periods of incubation, PI showed a decrease in the amounts of gonadotrophin and PRL released. Co-incubation of PHC or PI of intact or castrated rats with testosterone stimulated the release of LH and FSH during the first or second-24 hr incubation but inhibited the release of PRL in all the three incubations of 24 hr each. The extent of PRL inhibition increased with increasing incubation period. Testosterone had no effect on LHRH induced release of PRL but inhibited LHRH induced release of LH and FSH by pituitaries from constructs of normal rats. Testosterone reduced intrapituitary contents of PRL and FSH of intact and castrated rats. The data are interpreted to suggest that hypothalamus is essential for the maintenance of functional pituitary in vitro and that intrinsic differences exist in mechanisms regulating the secretion of LH, FSH and PRL.(ABSTRACT TRUNCATED AT 250 WORDS)     

Choice of extraction procedure for estimation of anterior pituitary hormone content

Searching for the best procedure for simultaneous estimation of the anterior pituitary hormones, extraction efficiencies of various media, additives such as urea and triton X-100, and physical treatments such as freezing-thawing (F-T) and sonication, were examined by measuring prolactin (PRL), growth hormone (GH), lutropin (LH), follitropin (FSH), and thyrotropin (TSH) in the extracts. Ethanolic media (60% EtOH) gave high yields of PRL at neutral to alkaline pH, but poor extraction of GH accompanied by a marked loss of its immunoreactivity during storage. Ethanolic media also gave a poor yield of LH even at high pH. Aqueous media like PBS at various pH, 0.1 M acetic acid and distilled water were considerably effective in the extraction of GH, LH, FSH and TSH if they were coupled with F-T and sonication. However, high yields of PRL could not be obtained with these aqueous media even with F-T and sonication. Hartree's 40% EtOH-6% ammonium acetate, pH 5.1, solubilized considerable amounts of glycoprotein hormones, but yielded almost no GH and only a small amount of PRL. The addition of triton X-100 to PBS (pH 7) at 0.1% resulted in the maximum extraction of glycoprotein hormones with homogenization and F-T, but further sonication was necessary for GH and PRL. When the anterior pituitaries were homogenized and frozen-thawed in PBS (pH 7) containing 1 M urea, yields of PRL, GH, LH, FSH, and TSH were maximum, and sonication did not cause any additional extraction, indicating that this procedure, i.e. homogenization and F-T in 1 M urea-PBS, would be the best for the simultaneous estimation of these anterior pituitary hormones.     

Comparison of pituitary responses to physical exercise in athletes and sedentary subjects

Serum growth hormone (GH), prolactin (PRL), cortisol, luteinizing hormone (LH), follicle-stimulating hormone (FSH) and thyroid-stimulating hormone (TSH) levels were evaluated before and after a bicycle ergometer exercise test in 8 male competitive volleyball players and in 8 sedentary healthy males of the same age. Increased serum GH and cortisol values after exercise in both groups were found, whereas an exercise-induced PRL release was observed in athletes only. Serum levels of LH, FSH and TSH were unaffected by the test in all subjects. A possible role of training in conditioning the hypothalamopituitary exercise-induced secretion is suggested.     

Luteinizing hormone releasing hormone mediates naloxone's effects on serum luteinizing hormone levels in normal and morphine-sensitized male rats

Naloxone produces large increases in serum luteinizing hormone (LH) levels in normal males and females, supporting a role for endogenous opioids (EOP) in the tonic inhibition of LH. Since the antagonist apparently exerts no important effects on the pituitary, the reasonable assumption has been made that it elevates gonadotropin levels by affecting the release of LH-releasing hormone (LHRH) from the hypothalamus. However, at present there is no direct in vivo evidence supporting this widely-held view. In an attempt to directly demonstrate that naloxone increases the secretion of LHRH, and thereby elevates serum LH levels, we examined whether a potent synthetic antagonist of LHRH ( [D-p Glu1, D-Phe2, D-Trp3,6]-LHRH, GPT-LHRH) blocked the effects of naloxone in male rats with a normal response to naloxone and in those with a markedly enhanced sensitivity to the drug induced by a brief period of morphine pellet implantation. Our results demonstrated that GT-LHRH antagonized equipotent doses of LHRH (100 ng/kg) and naloxone (0.5 mg/kg) over a similar time course with approximately the same AD50. Most importantly, however, we showed that the GPT-LHRH produced equivalent, parallel shifts to the right in the dose-response curves for LHRH and naloxone, indicative of competitive inhibition. We also found that GPT-LHRH completely abolished the enhanced response to naloxone's effects on LH which occurs in morphine-pretreated rats. Since we observed no competition between LHRH and naloxone for their binding sites in pituitary or brain, the only viable interpretation of our results is that naloxone increases LH by inducing the release of LHRH.     

Pancreatic polypeptides affect luteinizing and growth hormone secretion in rats

We have examined the effects of third cerebroventricular (3V) injections of avian and bovine pancreatic polypeptide (APP and BPP) and the C-terminal hexapeptide amide of human PP (CHPP) on the secretion of anterior pituitary hormones in conscious ovariectomized rats. Injection of APP (2.0 micrograms; 472 pmoles) or BPP (5.0 micrograms; 1191 pmoles) decreased plasma levels of luteinizing hormone (LH) when compared to pre-injection levels in these animals or to saline-injected controls. The lower dose of BPP (0.5 micrograms; 119 pmoles) decreased plasma LH versus pre-injection levels and control animals, however, these effects diminished at later times. Plasma growth hormone (GH) also decreased following 3V injections of APP (2.0 micrograms) or BPP (5.0 micrograms). The lower dose of BPP (0.5 microgram) initially inhibited GH release, however, this effect was rapidly reversed and GH levels were significantly greater than those in controls at 60 and 120 min. Injections of BPP or APP did not alter prolactin (PRL) or thyroid stimulating hormone (TSH) secretion. Administration of 2.0 micrograms and 0.2 microgram of CHPP (2488 and 249 pmoles) produced no significant effects on plasma LH, GH, PRL or TSH. APP and BPP had no consistent effects on hormone secretion from dispersed anterior pituitary cells. The results indicate that APP and BPP exert potent central effects which inhibit LH and GH release from the pituitary gland.     

Feedback regulation of growth hormone synthesis and secretion in fish and the emerging concept of intrapituitary feedback loop

Growth hormone (GH) is known to play a key role in the regulation of body growth and metabolism. Similar to mammals, GH secretion in fish is under the control of hypothalamic factors. Besides, signals generated within the pituitary and/or from peripheral tissues/organs can also exert a feedback control on GH release by effects acting on both the hypothalamus and/or anterior pituitary. Among these feedback signals, the functional role of IGF is well conserved from fish to mammals. In contrast, the effects of steroids and thyroid hormones are more variable and appear to be species-specific. Recently, a novel intrapituitary feedback loop regulating GH release and GH gene expression has been identified in fish. This feedback loop has three functional components: (i) LH induction of GH release from somatotrophs, (ii) amplification of GH secretion by GH autoregulation in somatotrophs, and (iii) GH feedback inhibition of LH release from neighboring gonadotrophs. In this article, the mechanisms for feedback control of GH synthesis and secretion are reviewed and functional implications of this local feedback loop are discussed. This intrapituitary feedback loop may represent a new facet of pituitary research with potential applications in aquaculture and clinical studies.     

Effects of prolonged treatment with diltiazem on pituitary secretion of luteinizing hormone, follicle-stimulating hormone, thyrotropin and prolactin.

In previous studies it has been observed that acute administration or short-term treatment with calcium channel blockers can influence the secretion of some pituitary hormones. In this study, we have examined the effect of the long-term administration of diltiazem on luteinizing-hormone (LH), follicle-stimulating hormone (FSH), thyrotropin (TSH) and prolactin (PRL) levels under basal conditions and after gonadotropin-releasing hormone (GnRH)/thyrotropin-releasing-hormone (TRH) stimulation in 12 subjects affected by cardiovascular diseases who were treated with diltiazem (60 mg 3 times/day per os) for more than 6 months and in 12 healthy volunteers of the same age. The basal levels of the studied hormones were similar in the two groups. In both the treated patients and the control subjects, a statistically significant increase (p < 0.01) in LH, FSH, TSH and PRL levels was observed after GnRH/TRH administration. Comparing the respective areas under the LH, FSH, TSH and PRL response curves between the two groups did not present any statistically significant difference. These findings indicate that long-term therapy with diltiazem does not alter pituitary hormone secretion.