Effect of zinc administration on thyrotropin releasing hormone-stimulated prolactinemia in healthy men

Previous in vitro studies have demonstrated zinc (Zn⁺⁺) inhibition of basal and of potassium (K⁺) or thyrotropin-releasing hormone (TRH)-stimulated prolactin (PRL) secretion, in a selective, reversible, and dose-dependent manner. Thus, Zn⁺⁺ may regulate physiologically pituitary PRL secretion. Furthermore, studies with patients with uremia, cirrhosis or prolactinoma, have shown the coexistence of hypozincemia and hyperprolactinemia and zinc supplementation did not correct hyperprolactinemia in these patients. In normal individuals Zn⁺⁺ administration produced controversial results on PRL secretion. Here, we investigated whether zinc administration affects TRH-stimulated PRL in healthy men. We found that Zn⁺⁺ administration does not change the TRH-stimulated PRL. Therefore, in normal conditions, Zn⁺⁺ does not inhibit TRH-stimulated prolactinemia. In addition, we found that acute increases of blood PRL and TRH do not alter blood Zn⁺⁺ levels.     

Prolactin release in polycystic ovarian syndrome

To evaluate the prevalence of hyperprolactinemia in patients with polycystic ovarian syndrome (PCO), 72 patients with oligo- or anovulation were studied. All of the patients had persisting elevated LH (greater than 25 mIU/ml), normal FSH, high LH/FSH ratio (greater than 2.5), and exaggerated LH responses to LHRH. Mean testosterone and androstenedione concentrations were appreciably increased in these patients. Out of 171 samples for prolactin (PRL) determination from these 72 patients, only 5 patients had a PRL value above 30 ng/ml during the first sampling. The next sampling from these same 5 women disclosed that they were transiently hyperprolactinemic because the next samples showed a normal PRL value. To further investigate the PRL secretory capacity 500 micrograms of TRH and 10 mg of metoclopramide (MCP) were administered to these 72 and 44 patients, respectively. The PRL response to MCP was significantly blunted in these patients compared to normal women while the PRL response to TRH in these patients was not indistinguishable from that in normal women. These results indicate that the true prevalence rate of hyperprolactinemia in PCO may be low rather than high and the association of hyperprolactinemia with PCO may be coincidental rather than a pathogenically related phenomenon.     

Self-priming effect of LH-RH on pituitary gonadotropins in hyperprolactinemic women

To investigate how various concentrations of serum prolactin (PRL) influence the priming effect of luteinizing hormone releasing hormone (LH-RH) on the pituitary gland, 24 women with various blood PRL concentrations received intravenous injections of 100 micrograms of synthetic LH-RH twice at an interval of 60 minutes and their serum LH and follicle-stimulating hormone (FSH) were measured and analysed. In the follicular phase with a normal PRL concentration (PRL less than 20 ng/ml, n = 6), marked first peaks of the two hormones following the first LH-RH stimulation and enhanced second peaks after the second LH-RH administration were observed, indicating a typical priming effect of LH-RH on gonadotropins, though the second response of FSH was more moderate than that of LH. In hyperprolactinemia, in which the serum PRL concentration was higher than 70 ng/ml (n = 13), the basal concentration of gonadotropins was not significantly changed but the priming effect of LH-RH on LH and FSH was significantly decreased (p less than 0.01). No marked second peaks of LH and FSH were observed, suggesting an inhibitory effect of hyperprolactinemia on the second release of LH and FSH. In contrast, this effect was restored in a group of women whose serum PRL concentration was between 30 and 50 ng/ml (n = 5). Furthermore, enhanced second peaks of both LH and FSH were noted after successful bromocriptine therapy reduced hyperprolactinemia (PRL greater than 70 ng/ml) to less than 25 ng/ml (n = 5).(ABSTRACT TRUNCATED AT 250 WORDS)     

Factors influencing resumption of meiotic maturation and cumulus expansion of porcine oocyte-cumulus cell complexes in vitro

The present study was undertaken to examine effects of various combinations of epidermal growth factor (EGF), transforming growth factor-b?₁ (TGF-b?₁), follicle-stimulating hormone (FSH), luteinizing hormone (LH), androstenedione (A₄), and estradiol-17b? (E₂) on meiotic maturation and cumulus expansion in the pig using an in vitro model system. Oocyte-cumulus cell complexes (OCC) were cultured in the media containing the abovementioned agents for 24 hr and were observed for germinal vesicle breakdown (GVBD), indicative of initiation of meiotic maturation, and for expansion of their cumulus cells. Treatment with EGF significantly increased (P < 0.05) incidence of GVBD, with maximal stimulation occurring at 1 ng/ml (55% vs. 12% in the control). Concentrations of EGF as low as 100 pg/ml significantly stimulated GVBD over control (37% vs. 12%). Addition of EGF (1 ng/ml) and FSH (1.5 μg/ml) together and LH (2 μg/ml) and FSH (1.5 μg/ml) together resulted in significantly higher (P < 0.01) GVBD levels than were observed in response to EGF, FSH, or LH alone. Addition of E₂ (1 μg/ml) had no effect by itself but significantly decreased the incidence of GVBD in the presence of FSH and of LH + FSH. Addition of A₄ (1 μg/ml) significantly reduced the percentage of oocytes undergoing GVBD when added alone or with FSH. Although both EGF and LH stimulated cumulus expansion, FSH was more effective in stimulating cumulus expansion than EGF or LH. TGF-b?₁ had no effect on GVBD or cumulus expansion. These studies indicate that these hormones may have differing roles in oocyte maturation and that their interactions may be part of an intricate system regulating the maturation of oocytes during follicular development in vivo. © 1993 Wiley-Liss, Inc.     

Hormonal regulation of testicular prolactin receptors and testosterone synthesis in golden hamsters

A study was conducted with hypophysectomized hamsters to determine effects of administration of prolactin (PRL), luteinizing hormone (LH), and follicle-stimulating hormone (FSH)-alone or in combination-on testicular PRL receptors and in vitro testosterone production. Hormonal injections commenced the second day after hypophysectomy, and hamsters were killed on Day 5, approximately 13 h after the last hormonal injection. PRL receptor numbers were reduced by hypophysectomy, and PRL administration alone lessened the extent of this decrease. By themselves, neither LH nor FSH affected PRL receptors, but a combination of PRL + FSH + LH produced the greatest effect on these receptors. Receptor affinity was only modestly affected by any treatments. In vitro testosterone synthesis was measured after addition of 0, 2, 10, and 50 mIU of human chorionic gonadotropin (hCG) to incubations of testicular tissue. Neither PRL nor FSH by themselves in vivo affected basal or hCG-stimulated testosterone production. However, PRL + FSH increased (p less than 0.05) the magnitude of the in vitro testosterone response to hCG, as well as the sensitivity of that response (slope of the dose-response curve). LH alone increased both basal and hCG-stimulated testosterone production. PRL + LH provided no additional increase in the magnitude of the testosterone response, but increased (p less than 0.05) the sensitivity. PRL + FSH + LH in vivo provided for the greatest sensitivity of the testosterone response to hCG.(ABSTRACT TRUNCATED AT 250 WORDS)     

Plasma Free Metanephrine and Normetanephrine Levels are Increased in Patients with Chronic Kidney Disease

ObjectivePatients with impaired renal function, particularly those on dialysis, frequently exhibit high blood pressure and hemodynamic instability, which often lead to pheochromocytoma assessment. Our objective was to assess plasma free metanephrine (MN) and normetanephrine (NMN) in chronic kidney disease patients (CKD) with or without dialysis.MethodsIn this prospective observational study we performed enzyme-linked immunosorbent assays (ELISAs) to evaluate plasma free MN and NMN in 48 CKD patients (15 with stage 3-5 CKD without dialysis, 26 on hemodialysis [HD], and 7 continuous ambulatory peritoneal dialysis [CAPD]), 30 patients with histologically proven pheochromocytoma, and 43 hypertensive patients. Adrenal masses were ruled out by abdominal computed tomography (CT) scans in all CKD and control hypertensive patients.ResultsAll 3 CKD groups (HD, CAPD, and CKD without dialysis) had significantly higher plasma free MN and NMN levels than the control hypertensive group (P < .0055). HD and CAPD patients had significantly lower plasma free NMN (P < .0055), but free MN levels were not significantly different than those observed in pheochromocytoma patients. In patients with HD, CAPD, and CKD without dialysis, plasma free MN and NMN were higher than manufacturer’s upper limits of normal in 57.7% and 28.5%, 13.3% and 61.5%, and 85.7% and 26.6%, respectively. Regression models showed that the number of dialysis years was significantly correlated with plasma free MN (r = 0.615, P < .001) but not free NMN.ConclusionPlasma free MN and NMN levels are frequently elevated in CKD patients, particularly in those on dialysis. Plasma free MN levels significantly overlap with the range in pheochromocytoma patients and correlate with the number of years on dialysis. (Endocr Pract. 2014;20:139-144)     

Intracellular dialysis disrupts Zn2+ dynamics and enables selective detection of Zn2+ influx in brain slice preparations

We examined the impact of intracellular dialysis on fluorescence detection of neuronal intracellular Zn²⁺ accumulation. Comparison between two dialysis conditions (standard; 20 min, brief; 2 min) by standard whole‐cell clamp revealed a high vulnerability of intracellular Zn²⁺ buffers to intracellular dialysis. Thus, low concentrations of zinc‐pyrithione generated robust responses in neurons with standard dialysis, but signals were smaller in neurons with short dialysis. Release from oxidation‐sensitive Zn²⁺ pools was reduced by standard dialysis, when compared with responses in neurons with brief dialysis. The dialysis effects were partly reversed by inclusion of recombinant metallothionein‐3 in the dialysis solution. These findings suggested that extensive dialysis could be exploited for selective detection of transmembrane Zn²⁺ influx. Different dialysis conditions were then used to probe responses to synaptic stimulation. Under standard dialysis conditions, synaptic stimuli generated significant FluoZin‐3 signals in wild‐type (WT) preparations, but responses were almost absent in preparations lacking vesicular Zn²⁺ (ZnT3‐KO). In contrast, under brief dialysis conditions, intracellular Zn²⁺ transients were very similar in WT and ZnT3‐KO preparations. This suggests that both intracellular release and transmembrane flux can contribute to intracellular Zn²⁺ accumulation after synaptic stimulation. These results demonstrate significant confounds and potential use of intracellular dialysis to investigate intracellular Zn²⁺ accumulation mechanisms.     

化疗对乳腺癌患者激素水平及月经状态的影响

目的:讨论乳腺癌患者术后辅助化疗对患者激素水平及月经状况的影响。方法:收集我院2014年1月-2015年8月初诊绝经前乳腺癌患者78例,绝经后乳腺癌患者50例,检测化疗前及化疗结束后的雌二醇(E2)、黄体生成素(LH)、卵泡刺激素(FSH)水平,随访绝经前乳腺癌患者化疗期间及化疗后月经变化情况。结果:绝经前乳腺癌患者化疗后E2水平明显下降,FSH、LH水平明显升高,差异具有统计学意义(P0.05),绝经后乳腺癌患者化疗后E2水平无明显变化(P0.05),FSH、LH水平均下降,差异具有统计学意义(P0.05)。绝经前乳腺癌患者三个不同年龄段化疗后E2水平降低,而FSH、LH水平升高,差异具有统计学意义(P0.05),但三个不同年龄段患者化疗前后性激素水平组间比较均无统计学差异(P0.05)。绝经前乳腺癌患者三个不同年龄段化疗后闭经率比较差异具有统计学意义(P0.05)。绝经前乳腺癌患者化疗后闭经患者E2水平明显低于未闭经患者,FSH、LH水平明显高于未闭经患者,差异具有统计学意义(P0.05)。结论:化疗可影响乳腺癌患者E2、FSH、LH水平,导致患者闭经,闭经情况与患者年龄有关。     

Effect of an LHRH Analog on Growth and Hormone Receptor Levels in DMBA-Induced Mammary Tumors in the Rat

Abstract

Dimethylbenz(a)anthracene (DMBA)-induced mammary tumors in the rat are well known to be hormono-dependent. Daily injections of an LHRH agonist, [D-Ala⁶, des-Gly-NH₂¹⁰]LHRH ethylamide (LHRH-A), 1 ug daily, for 38 days results in a 35% decrease in the number of tumors present at the beginning of the experiment compared to a decline of 45% after ovariectomy and of 8% in the control group. This is accompanied by a marked reduction in ovarian LH and FSH receptors. LHRH-A treatment also resulted in reduction in the number of progesterone and prolactin receptors in the tumors. In addition, an increase in plasma LH and FSH and a decline in plasma prolactin (PRL) concentrations are observed. The mechanisms by which the LHRH agonist induces its antitumoral effect probably relate to an ovarian desensitization to LH and FSH with a concomitant decrease in circulating levels of estrogen and prolactin, two well known stimuli for the growth of DMBA-induced mammary tumors.     

促排卵周期中未破裂黄素化卵泡综合征与性激素的关系探讨

目的:对未破裂黄素化卵泡综合征(LUFS)周期及正常排卵周期患者在不同时间性激素进行测定与比较,探讨LUFS的发生与性激素的关系。方法:对自然周期有排卵障碍的患者使用克罗米芬+HCG促排,分别在月经周期的第3天(C3)、第10天(C10)、卵泡成熟日(CM)(卵泡直径≥18mm)、尿LH阳性或注射HCG后48小时(CL)进行性激素测定,根据患者是否有排卵分为:正常排卵组(A组);未排卵出现LUFS组(B组)。选择同期自然周期正常排卵者为对照组(C组),同上法进行性激素测定。对A、B、C组患者不同时间的血清性激素进行比较。结果:1、FSH:在CM日A、B两组的促卵泡成熟激素(FSH)均低于C组(P<0.01)。2、LH:在C3、C10、CL日测定的A、B组LH值均高于C组(P<0.01),在CM日测定的A、B组LH值低于C组(P<0.01)。3、P:在CM日A、B两组的孕酮值低于C组(P<0.01);4、E2:在C3日测定的B组E2值低于C组(P<0.01),在CL日测定的B组E2值高于C组(P<0.01);5、PRL:在不同时间各组的PRL值均无显著性差异(P>0.05)。6、T:在不同时间各组的T值均无显著性差异(P>0.05)。结论:性激素在LUFS的发生中起重要作用,但以C3日E2值与LUFS的发生的关系最大,E2值低者易发生LUFS。     

Cellular associations of pituitary gonadotrophs in a rodent (Lagostomus maximus maximus) with photoperiod-dependent reproduction

The morphological characteristics and percentage of the cellular associations between gonadotrophs (LH- and FSH-secreting cells) and other cellular types were studied in pituitary pars distalis of adult male viscachas (Lagostomus maximus maximus) by double immunohistochemistry using specific antibodies to LH, FSH, PRL, GH, ACTH, TSH and S-100 protein (by folliculostellate cells; FSC), during long and short photoperiods. Bihormonal gonadotrophs were observed in ventro-medial and dorsal regions, interspersed between monohormonal gonadotrophs, and their number increased in short photoperiod. LH- and FSH-gonadotrophs were found around lactotrophs, enclosed by somatotrophs in the dorsal region, and associated with irregular corticotrophs. Gonadotrophs and thyrotrophs were associated along blood vessels and follicular structures. The cytoplasmic prolongations of FSC were in contact with both gonadotrophs. The percentage of LH–FSH, LH–ACTH, LH–FSC, FSH–LH, FSH–PRL, FSH–GH, FSH–ACTH, FSH–TSH and FSH–FSC associations decreased, whereas LH–PRL increased in short as compared to long photoperiod. The most abundant associations were LH–GH and LH–TSH during long photoperiod, but LH–GH and LH–PRL during short photoperiod. FSH–GH and FSH–PRL were the most numerous associations, and LH–FSC and FSH–FSC were the less abundant ones in both photoperiods. These results provide the morphological evidence for specific cellular associations between gonadotrophs and other cellular types of viscacha pituitary.     

Effects of human chorionic gonadotropin combined with clomiphene on Serum E2, FSH,LH and PRL levels in patients with polycystic ovarian syndrome

ObjectiveEffects of human chorionic gonadotropin combined with clomiphene on serum E₂, FSH, LH and PRL levels in patients with polycystic ovarian syndrome were analyzed.Methods90 patients with polycystic ovarian syndrome treated from January 2015 to March 2016 were randomly and evenly divided into control group and observation group. Patients in the control group were only treated with clomiphene. On the basis of the treatment in control group, human chorionic gonadotropin was added in the treatment of observation group. The changes of E₂, FSH, LH, PRL levels were compared between two groups before and after the treatment. Clinical curative effects of patients in the two groups was evaluated. Adverse reactions during treatment in two groups were observed and recorded. The incidence of adverse reactions was calculated.ResultsSerum E₂, FSH, LH and PRL levels in the two groups decreased significantly after treatment compared with that before treatment. The difference is statistical significant (P < 0.05). After the treatment, E₂, FSH, LH and PRL levels in the observation group were lower than that in the control group and the difference is statistical significant (P < 0.05). Total effective rate was 64.44% in the control group and 93.33% in the observation group. There were statistically significant difference in clinical curative effects in the two groups (P < 0.05). Different degrees of adverse reactions were found in both groups during treatment, such as nausea, vomiting, anorexia, liver dysfunction. There were 2 cases of nausea, 2 cases of vomiting, 3 cases of anorexia and 1 case of liver dysfunction from the 45 patients in control group. The total incidence of adverse reactions was 17.78% (8/45). There were 1 case of nausea, 1 case of vomiting, 1 case of anorexia and no liver dysfunction from the 45 patients in observation group. The total incidence of adverse reactions was 6.67% (3/45). The total incidence of adverse reactions in the observation group was significantly higher than that in the control group and the difference was not statistically significant (P > 0.05).ConclusionCombined use of human chorionic gonadotropin can significantly reduce serum E₂, FSH, LH and PRL levels, improve clinical curative effects and reduce the incidence of adverse reactions. Human chorionic gonadotropin has high application value on the treatment of polycystic ovary syndrome.     

Perioestrous patterns of circulating LH,FSH, prolactin and oestradiol-17β in the gilt

Concentrations of luteinizing hormone (LH), follicle stimulating hormone (FSH) and prolactin (PRL) were measured in jugular blood and those of oestradiol-17β (E₂17β) in utero-ovarian blood. Samples were taken from five intact gilts every 15 min for 108 h starting between day 15 and day 18 of the oestrous cycle. In the late luteal/early follicular phase, high pulsatile LH secretion, close to one pulse per hour, was observed. This could be the stimulus necessary for the final maturation of the ovarian follicles.Thereafter, frequency and amplitude of pulses, and the baseline value, decreased and were low at least between 36 and 12 h before the preovulatory LH surge. PRL and FSH concentrations also declined. This was probably due to the increase of oestrogen secretion. As E₂17β concentrations were still high, the surge of LH which was accompanied by increase in FSH and PRL, occurred for approximately 13 to 20 h. While LH and PRL mean levels decreased, FSH concentrations continued to increase. Peaks of PRL were observed during the late luteal/early follicular phase and during the LH discharge. During the period of estrus, each exposure to the boar was immediately followed by one of these peaks, which could play a role in the sexual behavior of the gilt.     

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.     

Urinary zinc and its relationships with microalbuminuria in type I diabetics

We investigated whether zincuria is associated with microalbuminuria in type I (insulin-dependent) diabetics (IDDM). In 169 IDDM, 215 overnight urine samples were collected for simultaneous assay of zinc and albumin. In 76 samples with excessive microalbuminuria (>15 mg/L), zincuria was higher than in the 139 other samples (0.83±0.06 vs 0.58±0.03 mg/Lp<0.001), though zincuria and microalbuminuria were not significantly correlated. An exercise provocation test was performed in 78 IDDM. Although microalbuminuria increased, zincuria did not change during the test. Another group of 83 IDDM underwent urinary zinc determination over a period of 1 h of recumbency. The 48 patients who had a zincuria higher than the mean+2 SD of control values had higher microalbuminuria at rest (48±16 μg/min vs 12±2p<0.01) and after exercise (111±33 vs 42±14p<0.02) than the remaining 35 subjects. Both subgroups did not differ for zinc intake and zincemia. Thus, incipient nephropathy as detected by the measurement of microalbuminuria is associated with a highly significant increase in zinc excretion, which is not proportional to albumin leakage, nor is it amplified during exercise. Hyperzincuria is not explained by an increase in zinc intake and does not result in hypozincemia.     

Characterization of a rat anterior pituitary cell bioassay

Summary We have described the protocols and characterization of a pituicyte culture, which became established as a reliable and reproducible bioassay for the secretion of follicle-stimulating hormone (FSH) and luteinizing hormone (LH). The bioassay was used to measure the bioactivity of factors that inhibit and stimulate gonadotrophin secretion. The protocol that was used involved the culling of female Wistar rats (200 to 250 g weight), at random stages of their cycle, and dispersal of their pituicytes in a concentration of 0.4 × 10⁶ cells · ml⁻¹ · well⁻¹ in serum-free medium (Dulbecco’s modified Eagle’s medium/Ham’s F12 mixture, supplemented with insulin and transferrin) in Falcon 3047 24-well culture plates. After 24 h of pre-culture, the medium was changed and the cells cultured for a further 48 h. The supernatant was removed and assayed for basal secretion of FSH and LH. The cells were then stimulated with 10⁻⁸ M GnRH for 4 h and the supernatant assayed for gonadotrophin-releasing hormone (GnRH)-stimulated FSH and LH secretion. All samples were assayed as pairs of duplicates (i.e. quadruplicate samples) which were randomly added to the plates to minimize plate effects. Random number tables were used to achieve this randomization.     

Effect of sampling interval on serum concentrations of luteinizing hormone, follicle-stimulating hormone, and prolactin in prepubertal, ovariectomized, and cycling gilts.

Three experiments were conducted to determine the effect of sampling interval on serum concentrations of LH, FSH, and prolactin (PRL) in prepubertal, ovariectomized, and cycling gilts. In all experiments, blood samples were drawn at 2-min intervals for 4 h from indwelling jugular catheters. Mean serum hormone concentrations, mean number of peaks, and mean and maximum peak heights of LH, FSH, and PRL were calculated using values reflecting 2-, 6-, 10-, 20-, 30-, and 60-min sampling intervals. For LH, FSH, and PRL, mean serum concentrations can be obtained through blood samples drawn at hourly intervals. Since LH peaks are very distinct in pigs, the number of secretory peaks and mean peak height can be obtained via samples drawn at 20-min intervals. Since FSH and PRL peaks are less well defined, a more frequent sampling interval (10 min) is needed to determine number of peaks and mean peak height. To obtain the maximum peak height or the number of minutes for LH, FSH, or PRL to rise from its nadir to zenith, blood samples need to be drawn at 2-min intervals. Regardless of reproductive state, these data indicate that the sampling interval needed to characterize serum concentrations of LH, FSH, and PRL in the gilt is dependent upon the parameter in question.     

Cyclosporine A inhibits the secretion of certain anterior pituitary hormones in patients with nephrotic syndrome.

To clarify the effects of cyclosporine A (CsA) on the secretion of serum thyrotropin (TSH), prolactin (PRL), luteinizing hormone (LH) and follicular stimulating hormone (FSH), we performed TRH and LH-RH testing in 4 patients with the nephrotic syndrome before and after the administration of CsA, 6 mg/kg/day for 4 to 12 weeks. Prior to CsA all patients responded normally to TRH with respect to TSH and PRL secretion. Two patients showed normal response of LH and FSH to LH-RH stimulation while the response in 2 other patients, who were both menopausal, was exaggerated. By the third or fourth week of CsA administration the basal and peak TSH and PRL values declined significantly in all patients in response to TRH stimulation while those of LH and FSH showed only a modest decrease in response to LH-RH stimulation. Two to 4 weeks after the cessation of CsA the response of TSH, PRL and FSH returned to the pretreatment level. These observations suggest that: 1) CsA exerts an inhibitory effect on the secretion of at least TSH and PRL in humans, and 2) the effect of CsA on the pituitary may be partially reversible after the cessation of the therapy.     

Mixed pituitary tumours--effects of bromocriptine treatment: Parlodel MR and Parlodel LAR.

Majority of pituitary tumours secrete one of the named hormones: PRL, GH, ACTH, proopiomelanocortine, alpha and beta subunit of TSH, LH, and FSH. Some of those tumours secrete two or more hormones. The aim of this study was to determine the effect of bromocriptine (Parlodel MR and LAR) upon secretion of hormones and tumour size in 10 patients with mixed pituitary tumours. In all patients pituitary and peripheral hormones, CT scan and visual fields were examined before and after treatment with bromocriptine: Parlodel MR and LAR. Bromocriptine treatment decreased PRL secretion in all 10 patients; GH--in all 6 in whom it was increased; TSH--in 2, FSH--in 2 and alpha-subunit in all 6 in whom they were increased. In 5 patients treatment resulted in shrinkage of the tumour mass by 20 to 35%. In all examined subjects clinical improvement was achieved. Our results demonstrate that bromocriptine (Parlodel MR and LAR) is very effective and well tolerated in the treatment of patients with mixed pituitary tumours particularly those with hyperprolactinemia.