In Cushing’s syndrome, there is an excess of cortisol secretion due to hyperfunction of the adrenal cortex. Hypersecretion of cortisol may be ACTH dependent or independent. The latter is present in an adrenal adenoma/carcinoma or bilateral macronodular adrenal hyperplasia. In some of these patients cortisol secretion is driven by stimuli other than ACTH, such as gastric inhibitory polypeptide (...

We have tested the participation of endogenous opiate pathways in the negative feedback actions of gonadal steroids on pulsatile properties of luteinizing (LH) hormone release in normal men. To this end, sex steroid hormones were infused intravenously at dosages that under steady state conditions selectively suppressed either the frequency or the amplitude of the pulsatile LH signal. The proper...

Genetic variants of human LH caused by amino acid replacements in the beta-subunit have been demonstrated to affect reproductive function. Occurrence of a G(1502)A substitution in the LHbeta gene leading to Gly(102)Ser replacement of the LHbeta protein has been found to be associated with infertility in the Singapore Chinese population. In the present study, a search for this LHbeta allele from...

The structure-stabilizing effect of homologous and heterogeneous desensitization and albumin on rat ovarian LH/hCG receptors was analyzed by thermal perturbation technique. HCG-induced down-regulation shifted the heat inactivation profile of hCG-binding sites to a temperature lower by about 7 degrees C (T50 values). In heterogeneous desensitization, which also involves uncoupling of receptors f...

Introduction: Previous studies have shown that stimulation of lateral hypothalamus (LH) produces antinociception. Orexin-A (OXA) receptor is strongly expressed in the nucleus locus coeruleus (LC) and orexinergic fibers densely project from LH to LC. In this study, we assessed the role of LC and its OXA receptors in antinociceptive response induced by LH chemical stimulation in the rat. Meth...

In previous studies the effect of endogenous opioid peptides (EOP) on LH secretion was mainly considered at the hypothalamic level, while opioid involvement in the modulation of LH secretion at the pituitary level remains insufficiently elucidated. Therefore, the present study was undertaken to determine the expression of genes encoding opioid precursors--proopiomelanocortin (POMC), proenkephal...

We report the case of an infant who presented at birth with a hypoplastic phallus associated with hypospadias. Low testosterone production, normal serum levels of steroid precursors, and increased LH in response to LH-releasing hormone supported a defect in Leydig cell differentiation or function. Conventional microscopic study of the testes showed fibroblastic cells in the interstitium. Howeve...

Progesterone (P) powerfully inhibits gonadotropin-releasing hormone (GnRH) secretion in ewes, as in other species, but the neural mechanisms underlying this effect remain poorly understood. Using an estrogen (E)-free ovine model, we investigated the immediate GnRH and luteinizing hormone (LH) response to acute manipulations of circulating P concentrations and whether this response was mediated ...

High oral doses of atrazine (ATRA) disrupt normal neuroendocrine function, resulting in suppression of the luteinizing hormone (LH) surge in adult, ovariectomized (OVX) estrogen-primed female rats. While the mechanism by which ATRA inhibits LH secretion is not known, current data indicate that ATRA does have anti-estrogenic properties in vitro and in vivo. In the body, ATRA is rapidly converted...

Undifferentiated granulosa cells from prehierarchal (6- to 8-mm-diameter) hen follicles express very low to undetectable levels of LH receptor (LH-R) mRNA, P450 cholesterol side chain cleavage (P450scc) enzyme activity, and steroidogenic acute regulatory (StAR) protein, and produce negligible progesterone, in vitro, following an acute (3-h) challenge with either FSH or LH. It has previously bee...