Testosterone (Te) concentrations fall gradually in healthy aging men. Postulated mechanisms include relative failure of gonadotropin-releasing hormone (GnRH), luteinizing hormone (LH), and/or gonadal Te secretion. Available methods to test Leydig cell Te production include pharmacological stimulation with human chorionic gonadotropin (hCG). We reasoned that physiological lutropic signaling coul...

Direct sampling of the human spermatic veins has disclosed concomitant LH and testosterone (T) pulses, suggesting pulsatile LH concentration-dependent stimulation of T secretion. However, studies to date have examined this hypothesis using only pharmacological stimulation with hCG. The present study tests the hypothesis that age is marked by decreased T secretory responses to repeated near-phys...

In two experiments with ovariectomized ewes, the plasma levels of LH and FSH were measured following passive immunization against LH-RH. The pulsatile secretion of LH was inhibited and the levels of the hormone fell quickly and were undetectable within 24 h. The levels of FSH fell more slowly and were always detectable. In the second of the experiments, pulses of LH of normal amplitude were re-...

We examined the immunohistochemical localization of luteinizing hormone (LH)/human chorionic gonadotrophin (HCG) receptor (LH-R) in the human ovary using the anti-human LH-R monoclonal antibody, 3B5. In the antral follicles, LH-R was detected on theca interna cells. In pre-ovulatory follicles, granulosa cells also expressed LH-R. During corpus luteum formation, granulosa cells seemed to increas...

We have investigated the effects of ovariectomy (OVX) and photostimulation (PS) on anterior pituitary LH beta mRNA abundance and circulating levels of LH in the domestic turkey. The birds were divided into the following four treatment groups: non-PS SHAM, PS SHAM, non-PS OVX, and PS OVX. Photostimulation was initiated 7 days after OVX. Anterior pituitaries and blood samples were collected on Da...

Endometrial cancer (EC) is a hormone-dependent cancer that currently represents the most frequent malignancy of the female reproductive tract. The involvement of steroid hormones in EC etiology and progression has been reported. More recently, gonadotropins, and, in particular LH/hCG, are emerging as novel regulators of tumor progression. In the present review, we discuss the role of the LH/hCG...

Adult female rats were rendered anovulatory by continuous illumination. Pituitary LH of these constant estrous rats decreased with the time length of illumination. Acidic extract from the rat hypothalamus was injected into these rats through the carotid artery for testing LH-RF activity. The extract, if a dose more than 2 hypothalamic fragments per rat was given, induced ovulation. Ovulatory re...

Spontaneous physical activity (SPA) describes activity outside of formal exercise and shows large interindividual variability. The hypothalamic orexin/hypocretin peptides are key regulators of SPA. Orexins drive SPA within multiple brain sites, including rostral lateral hypothalamus (LH) and nucleus accumbens shell (NAcSh). Rats with high basal SPA (high activity, HA) show higher orexin mRNA ex...

A variety of studies in man and animals demonstrate that testosterone (T) is aromatized to estradiol (E) in the hypothalamus and limbic system. These observations suggested the possibility that conversion to E is an absolute requirement for the biologic activity of T on the hypothalamic-pituitary axis. Since this hypothesis implies a common mechanism of action of these two steroids, the demonst...

Luteinizing hormone (LH) has been shown to be the only hormone essential for maintenance of testicular testosterone pr0duction.l LH mediates its effect on testicular steroidogenesis by binding to high affinity receptors in the plasma membrane of Leydig cells. In recent years, numerous investigators have reported that in vivo administration of LH or human chorionic gonadotropin (hCG) results in ...