Effects of gonadectomy on prolactin and LH secretion and the pituitary-thyroid axis in male dogs

The effects of gonadectomy on the secretion of prolactin, LH, TSH, and thyroxine were investigated. Blood serum hormone concentrations were analysed before and at 20, 120, and 180 min after a single iv TRH injection in each of eight healthy intact and castrated male beagle dogs before (control) and after 4-week treatment with the dopamine-2 receptor agonist cabergoline. Under control conditions the mean prolactin, TSH, and thyroxine concentrations were similar in intact and gonadectomised dogs, and administration of TRH provoked a significant (p < 0.01) increase in concentrations of the three hormones. The overall inhibitory effect of cabergoline treatment on prolactin secretion was more pronounced in the castrated dogs compared with the intact group. Cabergoline significantly suppressed the TRH-induced prolactin increase in each group (p < 0.01). Corresponding TRH-stimulated TSH concentrations were not affected by cabergoline. In the gonadectomised dogs, thyroxine concentrations before and at 120 and 180 min after TRH injection were significantly lower than under control conditions. LH concentrations were always higher (p < 0.01) in gonadectomised dogs compared with the intact dogs, but appeared to be affected neither by TRH nor by cabergoline administration. It can thus be concluded from the results, that gonadectomy does not result in hyperprolactinaemia in male dogs, while LH concentrations are significantly increased due to missing androgen feedback. Thyroid function remains unaffected by gonadectomy. Testicular steroids appear to interact with central dopaminergic and probably other neuroendocrine mechanisms regulating the secretion of prolactin, TSH, and thyroxine. Thus, long-term dopamine-2 receptor agonistic treatment may lead to a hypothyroid condition in castrated male dogs. (c) 2009 Elsevier B.V. All rights reserved.

Conditional deletion of hypothalamic Y2 receptors reverts gonadectomy-induced bone loss in adult mice

Reduction in levels of sex hormones at menopause in women is associated with two common, major outcomes, the accumulation of white adipose tissue, and the progressive loss of bone because of excess osteoclastic bone resorption exceeding osteoblastic bone formation. Current antiresorptive therapies can reduce osteoclastic activity but have only limited capacity to stimulate osteoblastic bone formation and restore lost skeletal mass. Likewise, the availability of effective pharmacological weight loss treatments is currently limited. Here we demonstrate that conditional deletion of hypothalamic neuropeptide Y2 receptors can prevent ongoing bone loss in sex hormone-deficient adult male and female mice. This benefit is attributable solely to activation of an anabolic osteoblastic bone formation response that counterbalances persistent elevation of bone resorption, suggesting the Y2-mediated anabolic pathway to be independent of sex hormones. Furthermore, the increase in fat mass that typically occurs after ovariectomy is prevented by germ line deletion of Y2 receptors, whereas in male mice body weight and fat mass were consistently lower than wild-type regardless of sex hormone status. Therefore, this study indicates a role for Y2 receptors in the accumulation of adipose tissue in the hypogonadal state and demonstrates that hypothalamic Y2 receptors constitutively restrain osteoblastic activity even in the absence of sex hormones. The increase in bone formation after release of this tonic inhibition suggests a promising new avenue for osteoporosis treatment.

Regulation and Function of GATA Transcription Factors in Adrenocortical Tumors and Granulosa Cells

Transcription factors play a key role in tumor development, in which dysfunction of genes regulating tissue growth and differentiation is a central phenomenon. The GATA family of transcription factors consists of six members that bind to a consensus DNA sequence (A/T)GATA(A/G) in gene promoters and enhancers. The two GATA factors expressed in the adrenal cortex are GATA-4 and GATA-6. In both mice and humans, GATA-4 can be detected only during the fetal period, whereas GATA-6 expression is abundant both throughout development and in the adult. It is already established that GATA factors are important in both normal development and tumorigenesis of several endocrine organs, and expression of GATA-4 and GATA-6 is detected in adrenocortical tumors. The aim of this study was to elucidate the function of these factors in adrenocortical tumor growth. In embryonal development, the adrenocortical cells arise and differentiate from a common pool with gonadal steroidogenic cells, the urogenital ridge. As the adult adrenal cortex undergoes constant renewal, it is hypothesized that undifferentiated adrenocortical progenitor cells reside adjacent to the adrenal capsule and give rise to daughter cells that differentiate and migrate centripetally. A diverse array of hormones controls the differentiation, growth and survival of steroidogenic cells in the adrenal gland and the gonads. Factors such as luteinizing hormone and inhibins, traditionally associated with gonadal steroidogenic cells, can also influence the function of adrenocortical cells in physiological and pathophysiological states. Certain inbred strains of mice develop subcapsular adrenocortical tumors in response to gonadectomy. In this study, we found that these tumors express GATA-4, normally absent from the adult adrenal cortex, while GATA-6 expression is downregulated. Gonadal markers such as luteinizing hormone receptor, anti-Müllerian hormone and P450c17 are also expressed in the neoplastic cells, and the tumors produce gonadal hormones. The tumor cells have lost the expression of melanocortin-2 receptor and the CYP enzymes necessary for the synthesis of corticosterone and aldosterone. By way of xenograft studies utilizing NU/J nude mice, we confirmed that chronic gonadotropin elevation is sufficient to induce adrenocortical tumorigenesis in susceptible inbred strains. Collectively, these studies suggest that subcapsular adrenocortical progenitor cells can, under certain conditions, adopt a gonadal fate. We studied the molecular mechanisms involved in gene regulation in endocrine cells in order to elucidate the role of GATA factors in endocrine tissues. Ovarian granulosa cells express both GATA-4 and GATA-6, and the TGF-β signaling pathway is active in these cells. Inhibin-α is both a target gene for, and an atypical or antagonistic member of the TGF-β growth factor superfamily. In this study, we show that GATA-4 is required for TGF-β-mediated inhibin-α promoter activation in granulosa cells, and that GATA-4 physically interacts with Smad3, a TGF-β downstream protein. Apart from the regulation of steroidogenesis and other events in normal tissues, TGF-β signaling is implicated in tumors of multiple organs, including the adrenal cortex. Another signaling pathway found often to be aberrantly active in adrenocortical tumors is the Wnt pathway. As both of these pathways regulate the expression of inhibin-α, a transcriptional target for GATA-4 and GATA-6, we wanted to investigate whether GATA factors are associated with the components of these signaling cascades in human adrenocortical tumors. We found that the expression of Wnt co-receptors LRP5 and LRP6, Smad3, GATA-6 and SF-1 was diminished in adrenocortical carcinomas with poor outcome. All of these factors drive inhibin-α expression, and their expression in adrenocortical tumors correlated with that of inhibin-α. The results support a tumor suppressor role previously suggested for inhibin-α in the mouse adrenal cortex, and offer putative pathways associated with adrenocortical tumor aggressiveness. Unraveling the role of GATA factors and associated molecules in human and mouse adrenocortical tumors could ultimately contribute to the development of diagnostic tools and future therapies for these diseases.

Differential vascular adaptive response to stress exposure in male and female rats: Role of gonadal hormones and endothelial cells

Although there are reports concerning a vascular adaptive response to stress in males, this is not yet defined in females. The aim of this study was to delineate functional gender differences in the rat vascular adaptive response to stress and to determine the ability of sex hormones to modulate the stress-induced vascular adaptive response. Responses to noradrenaline were evaluated in aortas, with and without endothelium, from intact, gonadectomized and gonadectomized-hormone-replaced males and females submitted or not to stress (2-h immobilization). Reactivity of the aorta of stressed and non-stressed intact males and females (n = 6-14 per group) was also examined in the presence of L-NAME or indomethacin. Stress decreased and gonadectomy increased maximal responses to noradrenaline in aortas with intact endothelium from both genders. Stress also reduced noradrenaline potency in males. In females, but not males, stress decreased the gonadectomy-induced noradrenaline hyper-reactivity to near that of intact non-stressed rats. Hormone replacement restored the gonadectomy-induced impaired vascular adaptive response to stress. L-NAME, but not indomethacin, abolished the stress-induced decrease in aorta reactivity of males and females. None of the procedures altered reactivity of aortas denuded of endothelium. Conclusion: Stress-induced vascular adaptive responses show gender differences. The magnitude of the adaptive response is dependent on testicular hormones and involves endothelial nitric oxide-system hyperactivity.

Gonadectomia pré-puberal em cães e gatos

A população de cães e gatos errantes é um problema grave de saúde pública e bem estar animal e a gonadectomia pré-puberal a partir de seis semanas de idade é a base para controle populacional efetivo. Os efeitos benéficos e maléficos são discutidos nesta revisão, auxiliando o médico veterinário a obter conhecimento e fundamentação científica para análise crítica do tema, propagação dessa prática e conscientização de proprietários.

EFFECT OF TESTOSTERONE ON THE PRESSOR-RESPONSE TO COMMON CAROTID OCCLUSION IN GONADECTOMIZED CONSCIOUS MALE-RATS WITH LESION OF THE MEDIAN-EMINENCE

The influence of testosterone on the development of the pressor response to common carotid occlusion was investigated in control and median eminence-lesioned male rats. In control rats (N = 9), gonadectomy performed 21 days before the experiments reduced by 22% (from 51 +/- 2 to 40 +/- 2 mmHg) and treatment with testosterone (300-mu-g for 4 days before the measurements) increased the initial peak pressor response (from 51 +/- 2 to 57 +/- 2 mmHg) which depends on carotid innervation. The maintained response which is of central origin (probably ischemic) was less affected. In nongonadectomized rats (N = 6), lesions of the median eminence (6 days) decreased the initial peak by 19% (from 52 +/- 2 to 42 +/- 3 mmHg) and the maintained response by 56% (from 32 +/- 2 to 14 +/- 1 mmHg). Sham-operated rats served as controls. In gonadectomized animals (N = 6) the lesion reduced only the maintained response (from 23 +/- 2 to 11 +/- 1 mmHg). Testosterone supplementation restored the maintained response but did not alter the initial peak. These results indicate that the pressor response to common carotid occlusion in male rats is modulated by testosterone and that the depression in the maintained response caused by median eminence lesion can be reversed by steroid supplementation.

Diagnosis of 5α-reductase type 2 deficiency: Contribution of anti-Müllerian hormone evaluation

Aim: To evaluate anti-Müllerian hormone (AMH) levels in patients with clinical and molecular diagnosis of 5α-reductase 2 deficiency. Patients and methods: Data from 14 patients whose age ranged from 21 days to 29 years were analyzed according to age and pubertal stage. Sexual ambiguity was rated as Prader III in 11 patients. LH, FSH, testosterone (T), dihydrotestosterone (DHT) and AMH serum levels were measured in all but two patients, who had been previously submitted to gonadectomy; T and DHT were also measured in 20 age-matched controls. Results: Gonadotropin levels were normal in all but one patient who retained gonads (six of whom had reached puberty) and T/DHT ratio was elevated in all patients when compared to controls. All prepubertal patients had AMH levels < -1 SD for age, while most pubertal patients had AMH levels compatible with pubertal stage. Conclusions: Prepubertal patients with 5α-reductase 2 deficiency have AMH values in the lower part of the normal range. These data indicate that T does not need to be converted to DHT to inhibit AMH secretion by Sertoli cells. © Freund Publishing House Ltd., London.

Prevalência do gene TSPY em pacientes com anomalias do desenvolvimento sexual no Pará

Pacientes portadores de Distúrbios da Diferenciação Sexual (DDS) apresentam maior risco de desenvolver neoplasias. As alterações neoplásicas mais frequentes nestes pacientes são: o gonadoblastoma, o carcinoma in situ/tumores de células germinativas intra-tubulares não classificados. As células germinativas tipo II são as percussoras destas lesões na maioria dos casos. O gonadoblastoma é uma neoplasia benigna que não metastiza, mas pela alta prevalência e risco de evolução para as formas malignas de neoplasias gonadais, merece especial atenção. Em uma região próxima ao centrômero no braço curto do cromossomo Y, foi mapeado o gene TSPY, imputado como o gene do gonadoblastoma. Este gene expressa-se em grande quantidade nas células que constituem o gonadoblastoma. Foram avaliados 47 pacientes com DDS nos seus cariótipos e na pesquisa da prevalência do TSPY através da técnica da reação em cadeia de polimerase (PCR). As análises revelaram que 50% das pacientes com síndrome de Turner, mesmo sem o cromossomo Y, íntegro ou não, evidente no cariótipo, foram positivas para a presença do gene TSPY. Estes dados evidenciam a importância da investigação do referido gene no acompanhamento e orientação de gonadectomia em pacientes com DDS.

Sindrome da insensitività completa agli androgeni e massa ossea. Valutazione basale e longitudinale dopo oltre 12 mesi di terapia estrogenica

L’osso è un tessuto target per estrogeni ed androgeni ma l’azione singola e la sinergia tra i due non sono compresi interamente. Le donne affette da Sindrome da Insensititvità Completa agli Androgeni (CAIS) hanno un cariotipo 46XY ma presentano una completa inattività del recettore degli androgeni. Nello studio abbiamo valutato la densità minerale ossea (BMD) in un gruppo di donne adulte CAIS sottoposte a gonadectomia al momento della prima visita e dopo almeno 12 mesi di terapia estrogenica. Il principale obiettivo è stato di valutare se, nelle donne CAIS, una ottimale estrogenizzazione fosse sufficiente a mantenere/ripristinare una adeguata BMD. 24 donne CAIS sono state sottoposte a DXA lombare e femorale all'arruolamento nello studio (t1), dopo terapia estrogenica di 12mesi(t2) e oltre (t>2). Sono state valutate: BMD(g/cm2) e Zscore lombare e femorale (a t1,t2 e t>2) E’ stato considerato se fossero rilevanti l’essere (gruppo1) o meno (gruppo 2) in terapia ormonale al t1 e l’età della gonadectomia. Risultati: Al t1 BMD e Zscore lombari e femorale erano significativamente ridotti rispetto alla popolazione controllo nel campione totale (lombare 0,900+0,12; -1,976+0,07, femorale 0,831 + 0,14; -1,385+0,98), nel gruppo 1 (lombare 0,918+0,116;-1,924+0,79, femorale 0,824+0,13;-1,40+1,00) e nel gruppo 2 (lombare 0.845+0,11 -2,13+1,15, femorale 0,857+0,17;-1,348+1,05) Al t2 e t>2 la BMD lombare è risultata significativamente aumentata (p=0,05 e p=0,02). Zscore lombare, BMD e Zscore femorale non hanno dimostrato variazioni significative. L’aver effettuato la gonadectomia in età post puberale è associato a Zscore lombare e femorale più elevati al t1. Nelle donne CAIS la terapia estrogenica è indispensabile per prevenire un'ulteriore perdita di BMD ma, da sola, non sembra in grado di ripristinare normali valori di BMD.I risultati del nostro studio supportano la tesi che gli androgeni, mediante l’azione recettoriale, abbiano un' azione diretta nel raggiungere e mantenere la BMD.

Endogenous estrogens, through estrogen receptor , constrain autoimmune inflammation in female mice by limiting CD4(+) T-cell homing into the CNS

Sex hormones influence immune responses and the development of autoimmune diseases including MS and its animal model, EAE. Although it has been previously reported that ovariectomy could worsen EAE, the mechanisms implicated in the protective action of endogenous ovarian hormones have not been addressed. In this report, we now show that endogenous estrogens limit EAE development and CNS inflammation in adult female mice through estrogen receptor expression in the host non-hematopoietic tissues. We provide evidence that the enhancing effect of gonadectomy on EAE development was due to quantitative rather than qualitative changes in effector Th1 or Th17 cell recruitment into the CNS. Consistent with this observation, adoptive transfer of myelin oligodendrocyte glycoprotein-specific encephalitogenic CD4(+) T lymphocytes induced more severe EAE in ovariectomized mice as compared to normal female mice. Finally, we show that gonadectomy accelerated the early recruitment of inflammatory cells into the CNS upon adoptive transfer of encephalitogenic CD4(+) T cells. Altogether, these data show that endogenous estrogens, through estrogen receptor , exert a protective effect on EAE by limiting the recruitment of blood-derived inflammatory cells into the CNS.

Mouse splenocyte proliferation and its modulation by sex steroids

Concanavalin A, a T cell mitogen enhanced DNA synthesis in murine splenocytes. Amongst the early signals prior to this event was an increase in cytosolic calcium derived from both intra- and extracellular sources. The requirements for extracellular calcium persisted for four hours after the lectin administration which itself was needed for six hours. Putative calcium channel antagonists and calmodulin inhibitors blocked ihe increase in DNA synthesis. The calcium signal was mimicked by application of the ionophore, A23187, although no increase in DNA synthesis occurred. An activator of protein kinase C, 12-0- tetradecanoylphorbol 13-acetate, had little effect in isolation but the combined application of these two agents greatly enhanced DNA synthesis. The natural mediators of these events are presumed to be inositol trisphosphate and diacylglycerol derived from phosphatidylinositol bisphosphate hydrolysis. Lectin application and protein kinase C activation both increased intracellular pH possibly as a result of Na'l'/H"'' exchange since amiloride an inhibitor of this antiporter inhibited lectin induced DNA synthesis. The calcium and hydrogen ionic changes occur within minutes of lectin application; the protracted requirement for this mitogen suggests further signalling mechanisms occur to elicit maximum DNA synthesis in these cells. Gonadectomy caused an increase in thymic and splenic weight. Spleno-cytes derived from castrated mice showed no change in mitogen response whereas those from ovariectomised mice demonstrated a reduced lectin sensitivity. Testosterone, 5 a dihydrotestosterone, a and 0 oestradiol all inhibited lectin induced DNA synthesis but only at pharmacological concentrations. Testosterone glucuronide and cholesterol were without effect Studies with mouse serum fractions of differing steroidal status were unable to confirm the presence or absence of serum factors which might mediate the effects of steroid on lymphoid cells, all fractions tested inhibited lymphocyte transformation. Both interleukin-2 and lipopolysaccharide induced splenocyte mitogene-sis was also impaired by high steroid concentrations in vitro, suggesting that steroids mediate their effect by a non-specific, non-receptor-mediated event.