Pituitary enlargement with suprasellar extension in functional hyperprolactinemia due to lactotroph hyperplasia: a pseudotumoral disease.

Beside the well characterized PRL-secreting adenomas, a wide spectrum of functional hyperprolactinemic states exists. We describe here five women, 21-38 yr old, all suspected of having a PRL-secreting adenoma because of a pseudotumoral appearance of the pituitary on computerized tomographic (CT) scan or magnetic resonance imaging (MRI). Four had oligomenorrhea with or without galactorrhea, one had amenorrhea with galactorrhea, and two complained of infertility. In the same patient, basal plasma PRL levels were variable on different days, sometimes normal (mean +/- SEM, 11.3 +/- 1.5 micrograms/L), sometimes elevated (49 +/- 7 micrograms/L), but in all cases, a PRL response of large amplitude to TRH (6- to 8-fold increase in the basal value) was observed. Basal plasma levels of estradiol were within luteal phase normal values (0.41 +/- 0.13 pmol/L), while progesterone levels were low (1.92 +/- 0.47 nmol/L). CT scan or MRI showed an intrasellar mass with suprasellar extension, suggesting a tumoral process. However, the signal intensity was homogeneous, and on coronal views, the suprasellar extension was pyramidal and symmetrical, and the pituitary stalk was always in the midline. The five patients were operated on by the transsphenoidal route, but no adenoma was found. Surgical biopsies were taken in four cases, and lactotroph hyperplasia, i.e. enlarged cell cords consisting mainly of PRL cells, was found in three of them. One case displayed a continuum between areas of lactotroph hyperplasia and adenomatous PRL cells. We conclude that functional hyperprolactinemia may mimic on CT scan or MRI a PRL-secreting adenoma.

A progesterone metabolite enhances the activity of the GABAA receptor complex at the pituitary level.

The interaction of 5 alpha-pregnane-3 alpha-ol-20-one (5 alpha 3 alpha P), a progesterone metabolite, with the GABAA receptor chloride channel complex was investigated at the pituitary level. In nanomolar concentrations this steroid potentiated the inhibitory effect of muscimol (a GABAA agonist) on prolactin release from rat pituitary cells in culture. In micromolar concentrations 5 alpha 3 alpha P had a direct inhibitory effect, similar to that of muscimol, with an IC50 value of 370 nM. This effect was antagonized by bicuculline, a GABAA antagonist, and by picrotoxin, a chloride ion channel blocker. Its reduced isomer, 5 alpha 3 beta P, and progesterone (Pg) were devoid of activity. Using [35S]t-butylbicyclophosphorothionate ([35S]TBPS) as a ligand, we demonstrated, for the first time, specific barbiturate sites on pituitary membranes, similar to those of the central nervous system, with a Kd value of 25 nM and a Bmax value of 62 fmol/mg protein. 5 alpha 3 alpha P inhibited the binding of [35S]TBPS. In contrast, its 3 beta isomer was inactive. These data show that 5 alpha 3 alpha P enhanced the activity of the GABAA receptor complex at the pituitary level and suggest that its inhibitory effect on prolactin release might be mediated by the barbiturate site or by a closely related site.

Inhibitory effect of 5 beta-pregnan-3 alpha-o1-20-one on gonadotropin-releasing hormone gene expression in the male rat.

Neuroanatomical data have documented the existence of synaptic contacts between gamma-aminobutyric acid (GABA) terminals and preoptic gonadotropin-releasing hormone (GnRH) neurons in the rat anterior hypothalamus. In addition, pharmacological studies have suggested that the GABAergic system may be involved in the control of gonadotropin release. Moreover, it has been shown that some progesterone metabolites such as 5 beta-pregnan-3 alpha-ol-20-one (5 beta 3 alpha P) are able to interact with the GABAA receptor complex. In the present study, we have investigated the effects of chronic (5 days) treatment with the GABAA-positive ligand 5 beta 3 alpha P (20 mg/kg body weight i.p., twice a day) or with the GABAA agonist muscimol (1 mg/kg body weight i.p., twice a day) alone or in combination on GnRH mRNA levels in the preoptic area of the male anterior hypothalamus as measured by in situ hybridization. Treatment with 5 beta 3 alpha P produced a 30% decrease in the number of grains overlying labelled cells, while muscimol treatment decreased the hybridization signal by 36%. The concomitant administration of 5 beta 3 alpha P and muscimol resulted in a 46% decrease in the GnRH mRNA levels. This inhibitory effect was completely antagonized by the concomitant administration of picrotoxin (4 mg/kg body weight i.p., twice a day). These data suggest that the GABAA receptor complex and steroids that interact positively with this GABAA receptor complex may play an important role in the regulation of GnRH biosynthesis by hypothalamic neurons.

A novel recognition site for somatostatin-14 on the GABA(A) receptor complex.

Functional interactions between gamma-aminobutyric acid (GABA) and somatostatin are suggested by the presence of synaptic contacts between GABA and somatostatin neurons, colocalisation of GABA and somatostatin and reciprocal modulation of somatostatin and GABA release. Nevertheless, a direct interaction of somatostatin with the GABA(A) receptor complex has not yet been investigated. A quantitative autoradiographic technique was used to determine the ability of somatostatin to interact with the [35S]t-butylbicyclophosphothionate [35S]TBPS binding sites of the GABA(A) receptor complex: somatostatin inhibited [35S]TBPS binding with IC50 values in the micromolar range in all brain regions studied. These results demonstrate for the first time a direct interaction between somatostatin and the GABA(A) receptor complex.

Treatment with dehydroepiandrosterone sulfate increases NMDA receptors in hippocampus and cortex.

Our aim was to investigate if the memory-enhancing effects reported for dehydroepiandrosterone sulfate in rodents could be mediated through modulation of NMDA receptors. Using autoradiography we studied the effect of dehydroepiandrosterone sulfate, administered for 5 days (30 mg/kg, i.p. twice a day), on NMDA binding sites labelled with [3H]dizocilpine ([3H]MK801) in rat brain. Dehydroepiandrosterone sulfate treatment significantly increased the [3H]MK801 binding sites in hippocampal areas (field CA1, CA3, dentate gyrus lateral blade and medial blade) and in cortex layer IV as compared to the control group. These results demonstrate for the first time the ability of dehydroepiandrosterone sulfate to increase the number of NMDA binding sites in rat brain, an action that could be of interest for therapeutic application.

Exaggerated prolactin response of thyrotropin-releasing hormone in women with anovulatory cycles: possible role of endogenous estrogens and effect of bromocriptine.

Twenty-one women 18 to 36 years old, presenting with chronic anovulation, were compared with 10 normally cycling women. The patients were characterized by low progesterone (P) levels (0.93 +/- 0.14 ng/ml versus 15.5 +/- 1.4 in controls), whereas 17 beta-estradiol (E2) was moderately decreased (110.2 +/- 8.3 pg/ml versus 162.8 +/- 14.5 in controls) realizing a relative hyperestrogenism. Basal prolactin (PRL) levels were not elevated (12.1 +/- 0.97 ng/ml versus 9.2 +/- 0.7 in controls), but after thyrotropin-releasing hormone (TRH) stimulation an exaggerated response was observed (114.5 +/- 7 ng/ml versus 55.8 +/- 9 in controls). Patients were treated with bromocriptine (1.25 mg 2 times a day) for 3 months. Fifteen responded with ovulatory cycles, and five became pregnant. Progesterone increased significantly (10.2 +/- 1.3 ng/ml), whereas in patients who did not ovulate P increased only slightly (1.56 +/- 0.18 ng/ml). The particular endocrine profile of these patients (P/E2 imbalance) realizing relative hyperestrogenism may be responsible for the exaggerated PRL response to TRH. Bromocriptine, in reducing this transient, or masked, hyperprolactinemia, allows in many patients the return to ovulatory cycles. This mechanism may be one of the possible pathways leading to chronic functional or organic hyperprolactinemia.

Comparison between the interaction of steroids with [35S]TBPS binding to cerebral cortical and to pituitary membranes: correlation with inhibition of prolactin release.

It has been shown previously that 5 alpha-pregnan-3 alpha-ol-20-one (5 alpha 3 alpha P) can inhibit prolactin release from anterior pituitary gland cells in culture through an interaction with a specific modulatory site on the GABAA receptor complex in anterior pituitary gland membranes. In the present work, this receptor site has been labelled with [35S]t-butylbicyclophosphorothionate ([35S]TBPS) to enable a study of the relative binding affinities (RBA) of different steroids for the GABAA receptor complex to be made. We have found a high correlation (r = +0.88) between the inhibition of [35S]TBPS binding to anterior pituitary membranes and the inhibition of [35S]TBPS binding to cerebral cortical membranes by nine different steroids. There was also a high correlation between the inhibition of prolactin release from anterior pituitary gland cells in culture by these steroids and the inhibition of [35S]TBPS binding to anterior pituitary membranes (r = +0.99) or to cortical membranes (r = +0.81). These observations suggest that the measurement of prolactin release from anterior pituitary gland cells in culture is a good indicator of the functional activity of drugs that bind to the allosteric modulatory TBPS-binding site on the GABAA-receptor complex.

An autoradiographic study comparing the interactions of 3 alpha-OH-5 alpha-pregnan-20-one, pregnenolone sulfate and pentobarbital with [3S]-TBPS binding sites and their modulation by GABA in different structures of the rat brain.

Using quantitative autoradiography, we have studied the distribution of the [35S]-TBPS binding sites of the GABA-A receptor complex in various structures of the rat brain. High densities of binding sites were observed in layer IV of the cerebral cortex, in the globus pallidus, and in the thalamus. Intermediate densities of binding sites were observed in superficial and deep layers of the cerebral cortex, in the dentate gyrus and in the hippocampus. For all of these structures, the interactions of 3 alpha-OH-5 alpha-pregnan-20-one (3 alpha 5 alpha P), pregnenolone sulfate (PS), and pentobarbital with [35S]-TBPS binding, in the presence or the absence of GABA were studied. In the absence of GABA, IC50 values for the inhibition of [35S]-TBPS binding were 10(-6) M for 3 alpha 5 alpha P and 10(-4) M for PS and pentobarbital in all of the brain regions studied. In the presence of GABA (5 x 10(-6) M), IC50 values were decreased by one order of magnitude for 3 alpha 5 alpha P, PS, and pentobarbital in all structures studied except layer IV of the cortex, where the IC50 value for PS was more markedly decreased (up to two orders of magnitude). By contrast, IC50 values for picrotoxin and TBPS to inhibit [35S]-TBPS binding were 10(-7) M and 10(-8) M, respectively, in the presence or absence of GABA.

Evidence that clomethiazole interacts with the macromolecular GABA A-receptor complex in the central nervous system and in the anterior pituitary gland.

Clomethiazole (CLOM) is known to be an anticonvulsant drug and has been also reported to decrease serum prolactin (PRL) in humans. Both effects may be mediated by an enhancement of gabaergic transmission. In order to determine if (CLOM) interacts with GABA metabolism and/or at the GABA receptor level, we studied its effect on PRL release and on the binding of various compounds that interact with the GABAA-benzodiazepine-receptor complex. Intraperitoneal (IP) administration of CLOM to rats significantly decreased PRL levels, and this effect was antagonized by IP administration of bicuculline, an antagonist of the GABAA receptor. In vitro, the inhibitory effect of muscimol on PRL release from rat hemiadenohypophysis was potentiated in a dose-dependent manner by preincubation with CLOM. This effect was antagonized by picrotoxin (10(-6) M). On the other hand, CLOM had no effect on GABA metabolism and did not compete with GABAA, GABAB or benzodiazepine binding sites in cortical membranes. CLOM competed, however, with the picrotoxin binding site labelled with [35S]-butylbicyclophosphorothionate (TBPS), at an IC50 value of 1.2 x 10(-4) M, which is in the same range as some barbiturates. These results concerning PRL release and binding experiments with cortical membranes suggest that CLOM interacts with the picrotoxin/barbiturate site of the GABAA-receptor-chloride channel complex.

Autoradiographic study of neurosteroid binding sites labelled with [35S]-TBPS in brain of different species.

Distribution of [35S]-TBPS binding sites was studied in various structures of brain in mouse and guinea pig and in cortex of monkey and in hippocampus of postmortem human brain. As it is observed for rat brain, high densities of [35S]-TBPS binding sites were found in layer IV of cortex in the four species, and in thalamus of mouse and guinea pig. Intermediate densities of binding sites were observed in superficial and deep layers of cortex in those four species and in hippocampus of mouse, guinea pig, and human. In all brain structures studied, 5 alpha 3 alpha P and picrotoxin produced a dose-dependent inhibition of [35S]-TBPS binding. No significant interregion or interspecies differences could not be detected for IC50 values of 5 alpha 3 alpha P or picrotoxin to inhibit [35S]-TBPS from its binding sites. In all regions studied, IC50 values were close to 1.5 x 10(-6) M for 5 alpha 3 alpha P and 2.3 x 10(-7) M for picrotoxin.

Differential effects of exogenous oestradiol and progesterone on mood in post-menopausal women: individual dose/effect relationship.

This study reports on 56 women who volunteered for consultation at a gynaecological hospital for their climacteric symptoms. The stability of their low oestradiol and high gonadotrophin plasma levels was controlled first. Afterwards they were treated for 3 mth with natural oestradiol (percutaneously). Once the plasma oestradiol levels were proved to be stable during the treatment, natural progesterone was also administered (orally) the last 10 days of treatment. As observed with all steroid administration, the same therapeutic regimen induced different individual plasma levels of the natural steroids. The relationship between mood and plasma levels was as follows. Moderate depressive symptoms were correlated to the lowest plasma oestradiol level, before and after treatment. Only when a moderate increase in oestradiol level was induced did the oestradiol treatment itself lead to a pleasant feeling of well-being. When an excessive increase was induced by the treatment, most of the women complained of unpleasant side effects, mostly irritability and aggressiveness. Progesterone had very few psychological effects if oestradiol levels were low or slightly increased. When plasma oestradiol was high, a moderate elevation of plasma progesterone induced a pleasant tranquillizing effect. A massive elevation of plasma progesterone levels immediately induced an inadequate hypnotic effect, sometimes with dizziness. Therefore, therapeutic administrations of natural steroids appear to strongly influence the mood and behaviour of post-menopausal women. However, the expected pleasant effect could not be successfully achieved without a careful adaptation of the correct dosage to each individual patient.

Modulation of central GABAA receptor complex by somatostatin: a pharmacological study.

The goal of the present study was to determine the possible interactions between somatostatin (SST) and gamma-aminobutyric acid (GABA). We thus investigated the SST interaction with [35S]-tertiary butylbicyclophosphorothionate (TBPS) binding sites of the cortical and hippocampal regions of the rat brain. The method used to identify such effects is in vitro quantitative autoradiography. Thus, the binding of the cage convulsant [35S]-TBPS to a picrotoxin-sensitive site in the rat brain was used to investigate the modulatory action of SST on the GABAA receptor complex. The addition of the peptide to the incubation medium results in a dose-dependent inhibition of [35S]-TBPS in cortical and hippocampal structures. Detailed analysis showed a dose-related effect of SST with relative potencies comparable to those observed for 5 alpha 3 alpha P and 5 beta 3 alpha P. In addition, these neurosteroids were able to enhance the efficacy of SST in inhibiting [35S]-TBPS binding. The efficacy of SST in enhancing the inhibitory action of neurosteroids was also evidenced. Furthermore, SST seems to mimic the effects of these neurosteroids as well as GABA and picrotoxin on [35S]-TBPS binding to the rat brain in every context examined. This suggests that somatostatin allosterically modifies [35S]-TBPS binding through a mechanism similar to that of GABA. On the other hand, a possible action of SST via transduction systems on the GABAA receptor complex could also be suggested. These results illustrate the importance of interactions in SST-mediated GABA transmission in these brain regions.

[The mechanism of action of cyproterone acetate in the treatment of hirsutism]. / Mécanisme d'action de l'acétate de cyprotérone dans le traitement de l'hirsutisme.

Cyproterone acetate (CPA) in association with percutaneously offinistered estradiol has been used for the treatment of 150 hirsute patients for periods ranging from 6 months to 3 years. A spectacular clinical improvement ensued. Plasma testosterone (T) and androstenedione (A) fell from 69 +/- 24 to 33 +/- 8 and 210 +/- 103 to 119 +/- 25 ng/dl (mean +/- SD) respectively after 3 months of treatment and remained low thereafter. In contrast, T glucuronide (Tg) and 3 alpha-androstanediol (Adiol) remained high during the whole course of treatment: 37 +/- 9 and 115 +/- 43 micrograms/24 h respectively. In vitro T 5 alpha-reductase activity (5 alpha-R) in pubic skin decreased from 147 +/- 34 to 79 +/- 17 fmol/mg skin after 1 year of treatment. To elucidate the discrepancy between plasma and urinary androgens levels, T production rate (PR) and metabolic clearance rate (MCR) were measured with the constant infusion technique in 6 patients before and after 6 months of treatment. PR decreased from 988 +/- 205 to 380 +/- 140 micrograms/24 h (mean +/- SD). In contrast MCRT increased from 1275 +/- 200 to 1632 +/- 360 1/24 h; this increase in MCRT explains the striking plasma T concentration fall and the high TG and Adiol excretion relative to the decrease in PR. Antipyrine clearance rate (n = 8) increased from 36.3 +/- 5.2 to 51.5 +/- 7.4 ml/min whereas urinary/6 beta hydroxycortisol remained unchanged. In conclusion, CPA acts through several mechanisms:(ABSTRACT TRUNCATED AT 250 WORDS)

[Treatment of hirsutism with cyproterone acetate and percutaneous estradiol]. / Traitement de l'hirsutisme par l'acétate de cyprotérone et l'estradiol percutané.

One-hundred and fifty hirsute women (68 with type I or II polycystic ovary syndrome and 82 with idiopathic hirsutism) were treated for periods of 6 to 48 months with oral cyproterone (CPA), a drug with peripheral antiandrogenic, antigonadotrophic and progestative properties, and 17 beta-estradiol given percutaneously to ensure estrogenic impregnation. CPA was administered in daily doses of 50 mg from day 5 to day 25 of the menstrual cycle, and E 2 (3 mg/day) from day 16 to day 25. The dramatic regression of hirsutism observed after 3 to 6 months of treatment was paralleled by a marked decrease of plasma testosterone and delta 4-androstenedione levels and a decrease of the androgen-dependent skin testosterone 5 alpha-reductase. The CPA-percutaneous E 2 combination also has contraceptive properties. Beside its remarkable therapeutic effectiveness, it has the advantages of avoiding the adverse reactions reported with higher doses of CPA and the metabolic and vascular effects of synthetic estrogen administered orally.