Amenorrea primaria por hipogonadismo hipogonadotropo normosómico / Primary amenorrhea due to hypogonadotrophic hypogonadism

Mujer de 17 años, adoptada, que consulta por retraso puberal completo. Presentaba un crecimiento armónico, con olfato normal y repercusión psicológica grave por ausencia completa de desarrollo puberal. El estudio hormonal basal confirma la presencia de hipoestrogenismo grave, ausencia de adrenarquia y valores de gonadotropinas en rango normal para primera mitad de la fase folicular. El resto de hormonas hipofisarias fueron normales. La resonancia magnética hipotálamo-hipofisaria fue normal. El estímulo con 100 g de hormona liberadora de hormona luteinizante indujo una respuesta normal de hormona folículo estimulante y hormona luteinizante, y la secreción nocturna (12 h) de gonadotropinas evidenció mínima pulsatilidad de hormona luteínizante, con aumento nocturno y menor pulsatilidad de hormona folículo estimulante, sin aumento nocturno. La paciente fue diagnosticada de hipogonadismo hipogonadotropo normosómico. Se inició inducción de pubertad con estrógenos en dosis progresivas, adición posterior de progesterona y, finalmente, anticonceptivos orales. A los 26 años, se plantea la fertilidad por lo que se revalúa y se confirma hipogonadismo hipogonadotropo parcial, con el mismo perfil de secreción de gonadotropinas, espontánea y en respuesta a hormona liberadora de gonadotropina. Se discuten las características clínicas, con especial atención al diagnóstico etiológico del hipogonadismo hipogonadotropo normosómico, a la luz de la nueva información sobre las bases moleculares del hipogonadismo hipogonadotropo idiopático. Asimismo, se discute el abordaje terapéutico del hipogonadismo hipogonadotropo (AU)

We describe the case of an adopted 17-year-old girl who consulted because of complete pubertal delay. No specific dysmorphic features were observed and olfaction was normal. The complete absence of pubertal development had severe psychological effects. Basal hormonal determinations confirmed severe hypoestrogenism, with serum gonadotropins within the normal range for the early follicular phase. Serum levels of other pituitary hormones were normal. A sellar magnetic resonance imaging (MRI) scan was normal. Both gonadotropins increased normally in response to gonadotropin-releasing hormone (GnRH) (100 g, IV). Spontaneous gonadotropin secretion through a 12-h nocturnal period showed minimal luteinizing hormone (LH) pulsatility with nocturnal increase and less follicle-stimulating hormone (FSH) pulsatility without nocturnal increment. A diagnosis of normosomic hypogonadotropic hypogonadism was made. The patient was treated with progressive doses of conjugated estrogens, with subsequent addition of progesterone in a cyclic regimen. Finally, oral contraception was prescribed. At 26 years of age, she desired fertility and was clinically reevaluated. Partial hypogonadotropic hypogonadism was confirmed, with similar patterns of spontaneous gonadotropin secretion and GnRH response. We discuss the clinical characteristics of this entity, focusing mainly on the cause of normosomic hypogonadotropic hypogonadism, in light of new information about the molecular bases of these disorders. The treatment of hypogonadotropic hypogonadism is also discussed (AU)

Sensitivity to exogenous GH and reversibility of the reduced IGF-I gene expression in aging rats.

BACKGROUND: IGF-I gene expression and IGF-I plasma concentration decline with age. A decreased sensitivity to GH has been suggested to be a contributory mechanism to this, in addition to attenuated GH secretion. OBJECTIVE: This study focuses on the sensitivity to exogenous GH and the reversibility of the reduced IGF-I gene expression in aging male rats. DESIGN: Three groups of male Wistar rats aged 3 months (young adult), 11 months (middle-aged) and 27 months (old), received recombinant human GH (rhGH) (150 microg/12 h s.c.) for seven consecutive days. RESULTS: This rhGH treatment completely reversed plasma immunoreactive IGF-I (IR-IGF-I) and hepatic IGF-I mRNA levels in 11-month-old and 27-month-old animals to the levels of the young group of animals. The sensitivity in the old group (percentage of increment after the same or lower dose of rhGH per body weight) was increased for both parameters; serum IGF-I increment: 15% in 3-month-old, 42.6% in 11-month-old and 119.1% in 27-month-old rats; and hepatic IGF-Ib mRNA increase: 45% in 3-month-old, 27.8% in 11-month-old and 64.3% in 27-month-old rats. IGF binding protein-3 (IGFBP-3) mRNA level in the liver was significantly decreased in the old group and only a partial reversion occurred in this group after rhGH treatment; the percentage of increment was also higher in the old group of rats. In extrahepatic tissues IGF-I mRNA was not significantly different in the kidney and the testis of the three groups, and the rhGH treatment produced a significant and similar increase of IGF-I mRNA level in the kidney of the three groups of rats and in the testis of the 27-month-old animals. The GHr/GHBP mRNA remained unchanged in the liver and in the kidney or the testis of the three groups, and was not influenced by the rhGH treatment. Exogenous rhGH decreased pituitary GH mRNA accumulation in a more intense manner in the old group versus control of each group: young adult, 25%; middle-aged, 41.2%; and old rats, 55%. The action of rhGH on pituitary immunoreactive GH (IR-GH) content was only significantly evident in the young group. CONCLUSIONS: These results establish that exogenous rhGH recovers the attenuated liver IGF-I gene expression and the diminished plasma IR-IGF-I in old rats to the levels of young adult animals. They also indicate that the hepatic and extrahepatic (kidney and testis) sensitivity to one established dose per weight of exogenous rhGH is not altered in old animals, or could be potentially increased in some tissues.

Transcriptional activation of the gonadotropin-releasing hormone receptor gene by activin A.

It has been reported that activin A stimulates the synthesis of the GnRH receptors (GnRHR) in rat pituitary cultures. However, the role of activin A in the regulation of the GnRHR gene at the molecular level is not known. In the present work, we have studied the regulation of the GnRHR gene by activin A in the gonadotrope cell line, alpha T3-1, where the GnRHR gene is highly expressed. First, we demonstrate that these cells express the mRNAs of three types of activin receptors: I, II, and IIB. Activin A increases GnRHR mRNA levels in a dose-and time-dependent manner, with maximal stimulation (2.5 +/- 0.5-fold) occurring with a dose of 20 ng/ml after 36 h of incubation. To ascertain whether this effect occurs at the transcriptional level, we performed nuclear run-off experiments in alpha T3-1 cells, which demonstrate a 1.6-fold increase in the levels of newly synthesized GnRHR mRNA in response to activin A. To investigate further the effect of activin A on the transcription of the GnRHR gene, alpha T3-1 cells were transiently transfected with a mouse GnRHR promoter/luciferase reporter gene (GnRHR-Luc) and challenged with activin A. Luciferase activity increases in response to activin A to the same extent (2.4 +/- 0.4-fold) and with similar dose-response and time-course profiles as the mRNA levels. Follistatin (100 ng/ml), a well known activin antagonist, completely abolishes the activin A effect on both mRNA levels and GnRHR-Luc activity. Follistatin also decreases the basal expression of the GnRHR gene by 33% as determined by GnRHR-Luc activity. This, together with our demonstration of the presence of the inhibin beta B-subunit mRNA in alpha T3-1 cells, suggests a potential paracrine/autocrine role of endogenous activin B on the regulation of the GnRHR gene in these cells. To provide evidence for biological significance of activin A stimulation of GnRHR gene expression, the response of a human gonadotropin alpha-subunit promoter/luciferase reporter gene (alpha Gon-Luc) to GnRH was assessed in alpha T3-1 cells pretreated with activin A. Activin enhances the stimulation of alpha Gon-Luc activity by GnRH by 1.6 +/- 0.4-fold. These data demonstrate that activin A can stimulate the expression of the GnRHR gene at the transcriptional level. Furthermore, transfection studies localize the activin responsive element to 1.2 kb of the 5'-flanking region of the GnRHR gene. Transcriptional activation of the GnRHR gene by activin A may serve as a mechanism for the modulation of gonadotrope responsiveness to GnRH.

Corticosterone modulates growth hormone-releasing factor and somatostatin in fetal rat hypothalamic cultures.

It is well known that chronic supraphysiological doses of glucocorticoids (GC) inhibit GH secretion in vivo, and stimulate GH secretion from the somatotropes in vitro. It has been suggested that GC exert an inhibitory role in the hypothalamus surpassing the GC-positive effect at the somatotrope level. To test the hypothesis that GC can affect growth hormone-releasing releasing factor (GRF) and somatostatin (SS) at the hypothalamic level, we studied the effect of corticosterone on the immunoreactive content of GRF (IR-GRF) and SS (IR-SS) in cells and media of fetal hypothalamic cells in culture. After 20 days in culture, cells were incubated with serum-free medium containing corticosterone (from 0.3 to 300 nM) for 48 h. Corticosterone had a dual effect on IR-GRF. Concentrations in the range of the glucocorticoid receptor Kd (3 nM) increased peptide content, whereas higher concentrations (30 and 300 nM) decreased IR-GRF content in cells and media. Conversely, corticosterone increased SS cell content, only at a concentration of 3 nM, inducing a 2- to 3-fold increment in media content with the highest doses (30 and 300 nM). These results demonstrated that both GRF and SS are modulated by corticosterone in primary fetal rat hypothalamic cultures. Whereas GRF exhibited a dual response, stimulatory and inhibitory, at low and high corticosterone doses, respectively, SS showed a parallel increase with the corticosterone concentrations.

Biosynthesis of growth hormone-releasing factor by fetal rat cerebrocortical and hypothalamic cells.

The biosynthesis of growth hormone-releasing factor (GRF) by cerebrocortical tissue is controversial. Although several reports have indicated its presence in certain rat cortical areas and in cultured rat hypothalamic cells, no data exist demonstrating its biosynthesis in these areas. In this study, we have investigated the capacity of fetal rat cerebrocortical and hypothalamic cells in culture for synthesizing GRF. Fetal cerebrocortical and hypothalamic cells were exposed to [3H]Arg for 48 h. Medium and cell extracts were processed and [3H]Arg-IR-rGRF was isolated by affinity chromatography and characterized by HPLC. Intracellular [3H]Arg-IR-rGRF from both hypothalamic and cerebrocortical cells exhibited four major peaks, one of them coeluting with synthetic rGRF. In cerebrocortical cultures, newly synthesized and released [3H]Arg-IR-rGRF showed a similar pattern to the cell content. However, in media from hypothalamic cells, higher hydrophobicity molecular forms were absent. The data demonstrated that fetal cerebrocortical and hypothalamic cells in primary culture synthesize GRF with similar posttranslational processing, but with different molecular patterns of secretion.

Growth hormone-releasing factor regulation by somatostatin, growth hormone and insulin-like growth factor I in fetal rat hypothalamic-brain stem cell cocultures.

Information about growth hormone-releasing factor (GRF) regulation by somatostatin, GH and IGF-I is scarce and controversial. This could be due to the in vivo interactions among these signals and the lack of models for individualizing the action of one of them from the others upon GRF regulation. The aim of the present work was to study GRF regulation by these signals, using primary fetal rat hypothalamic-brain stem cell cocultures. Coculturing of these two cytotypes increases hypothalamic immunoreactive rat GRF (IR-rGRF) content in cells by 45% and in media by 36%. The effect of SS on GRF in cocultures was examined by using a multiple approach: (1) depleting endogenous SS by adding 1 mM cysteamine (CSH); (2) blocking endogenous SS by incubation with SS antiserum, and (3) incubating with synthetic SS14 at different concentrations and exposure periods. 1 mM CSH depleted IR-SS content (pg/plate, mean +/- SE) in cells (CSH-treated: 68 +/- 8 vs. control: 322 +/- 10, p < 0.01) and media (CSH-treated: 211 +/- 15 vs. control: 880 +/- 70; p < 0.01). In the CSH-induced SS-depleted cultures, a slight reduction in the IR-rGRF content in cells was observed (CSH-treated: 93.5 +/- 4.5 vs. control: 111 +/- 6; p < 0.05), with no effect on media content. When SS antiserum was added to plates, there was a slight reduction in the IR-rGRF content in cells and media, but it was not significantly different from the controls. However, SS14 (10(-10)-10(-8) M) could not modify IR-rGRF content in media and cells. The GH effect on IR-rGRF was studied in the absence of CSH and in CSH-induced SS-depleted cultures. GH (5 microM, 24 h) decreased (52%) the IR-rGRF content in media (GH-treated: 28.7 +/- 4.6 vs. control: 60.2 +/- 7; p < 0.01) without causing changes in cell content. In SS-depleted cultures, the inhibitory action of GH on media IR-rGRF was greater (62% decrease) (GH-treated: not detected, control 56 +/- 10; p < 0.01) and also affected IR-rGRF cell content (GH-treated: 64.3 +/- 7.3 vs. control: 160 +/- 9.6; p < 0.01). In the same experiments, GH increased IR-SS content in cells (GH-treated: 31.8 +/- 4.6 vs. control 20.9 +/- 0.5; p < 0.01) and in media (GH-treated: 413 +/- 7 vs. control: 286 +/- 9; p < 0.01). 1 mM CSH again depleted IR-SS content and abolished the GH stimulatory effect.(ABSTRACT TRUNCATED AT 400 WORDS)

Depolarizing influences regulate somatostatin synthesis and processing in cultured cerebral cortical cells.

There is increasing evidence that persistent depolarization plays a critical role not only in excitation-secretion coupling, but also in the mechanisms linking excitation of neuronal cells to long-term adaptative changes in biosynthesis of neuropeptides. Somatostatin (SRIF) release and synthesis are affected by numerous agents, such as high concentrations of potassium that cause depolarization of cellular membrane. In the present work, we tried to determine whether prolonged exposure to veratridine (VTD) regulates SRIF synthesis. We found that exposure to VTD (100 microM) resulted in the stimulation of total (cell content + media) immunoreactive SRIF (IR-SRIF). This effect was calcium- and sodium-dependent, since it was prevented when verapamil (VPM) 20 microM or tetrodotoxin (TTX) 1 microM were added simultaneously with VTD. Cerebral cortical cells were exposed to high potassium concentrations, and the nature of the IR-SRIF was characterized by high-pressure liquid chromatography (HPLC) or gel filtration. It was evident that chronic exposure to high potassium concentrations modified the elution profile of medium IR-SRIF on HPLC and gel filtration, causing an increase in somatostatin-28 (S-28) and a decrease in somatostatin-14 (S-14). The results indicate that chronic exposure to VTD or high potassium concentration increases immunoreactive somatostatin and augments synthesis of its high-molecular-weight forms. This suggests that chronic membrane depolarization activating sodium and calcium channels initiates the entry of calcium ions, which triggers somatostatin release and causes a depletion of its intracellular stores. The stimulation of somatostatin secretion could be coupled to synthesis of the peptide.

Dopaminergic modulation of aldosterone secretion in the normal menstrual cycle.

A group of eight normotensive female volunteers with regular menstrual cycles were studied during two menstrual cycles: a control cycle and one in which they received lisuride, a D1-D2 dopamine agonist (0.025 mg/8 hr). The following tests were performed in both halves of both cycles: 1) the response of prolactin (PRL) to thyrotropin-releasing hormone (TRH) administration; 2) the response of plasma renin activity (PRA) and plasma aldosterone (PA) to furosemide for 2 hours in the upright posture; and 3) the response of PRL, PRA, PA, plasma potassium (K), and cortisol (F) to metoclopramide administration. An increased response of PRL to TRH and PA to furosemide in the upright position and to metoclopramide were found in the luteal phase of the control study (p less than 0.05). After lisuride administration, in the interphase, differences in the responses of PRL to TRH and PA to furosemide in the upright position disappeared, whereas that of PA to metoclopramide increased further. We conclude that the increase of aldosterone normally observed during the luteal phase of the menstrual cycle is at least partly conditioned by diminished dopaminergic tone and that the response of aldosterone secretion to furosemide-induced sodium depletion and its response to metoclopramide stimulation may be modulated by two different types of dopamine receptors.