Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “testosterone secretion”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 307 records · Page 17Linked to original sources
PubMed1978

[Demonstration of testosterone secretion by testicular tissue of hypophysectomized boar as affected by HCG in organ culture].

Boar Leydig cells undergo a strong atrophy from 1 to 3 months after hypophysectomy but can be reactivated by the gonadotropin HCG in organ culture conditions. This reactivation which appeared at histological and ultrastructural level was evidenced by the capacity of testicular tissue to synthesize testosterone as judged by radioimmunoassay. Both synthesis in the tissue and release into the medium increased according the incubation time with HCG; the adjonction of 17 alpha-OH-pregneolone to culture medium led to increase the intra and extra-tissular concentration of testosterone.

17-alpha-Hydroxypregnenolone↗
PubMed2006

Control of luteinizing hormone and testosterone secretion in a flexibly breeding male passerine, the Rufous-winged Sparrow, Aimophila carpalis.

Rufous-winged Sparrows, Aimophila carpalis, reside in the Sonoran desert and although testicular development is initiated in the spring under the influence of increasing day length, breeding occurs opportunistically in summer in association with heavy rainfall or "monsoon". The aim of this study in free-living male Rufous-winged Sparrows was to establish the relationship between concentrations of plasma luteinizing hormone (LH) and testosterone (T), and breeding associated with heavy rainfall, and to investigate whether breeding is mediated by changes in pituitary gland sensitivity to gonadotropin releasing hormone-I (GnRH) and the recently discovered avian gonadotropin-inhibitory hormone (GnIH). Concentrations of plasma LH and T were relatively low until mid-summer, but increased rapidly and transiently immediately prior to the monsoon which occurred after the summer solstice, when day lengths were decreasing. At this time the birds came into full breeding condition. An injection of chicken GnRH (10 ng) increased plasma LH within 2 min when given before or during the monsoon. An injection of GnIH (1 microg) did not affect plasma LH within 2 min during the monsoon and did not decrease GnRH-elicited LH secretion before or during the monsoon. No experimental treatment affected plasma T concentrations. The data suggest in male Rufous-winged Sparrows that the seasonal increase in plasma LH associated with summer monsoon results from increased stimulation of the pituitary gland by GnRH, rather than from a change in the responsiveness of the gland to GnRH, and that GnIH does not play an acute role in this mechanism. However, a possible chronic role for GnIH in the seasonal control of LH synthesis and secretion through an inhibitory effect on the hypothalamic GnRH system remains to be investigated.

Animals↗
PubMed1995

[Kinetic study of pulsatility of gonadotropin and testosterone secretion in normospermic fertile and infertile men with idiopathic oligo-asthenozoospermia].

Idiopathic oligo-asthenozoospermia is among the most frequent causes of male infertility and has a not very well understood etiopathogenesis. To obtain valuable information about the role of some endocrine factors in the etiology of this kind of infertility, information that is not easy obtain by the traditional analytical methods, we applied some recently proposed mathematical algorithms to analyze with more exactitude the importance of the secretory pulses of three hormones, luteinizing hormone (LH), follicle stimulating hormone (FSH) and testosterone (T). Serum samples were obtained every 10 min for 12 h, from 15 fertile normospermic men and 14 infertile patients with idiopathic oligo-asthenozoospermia; the concentration profiles of FSH and T were analyzed by IRMA and RIA, and the immuno-and bioactive LH concentrations were quantified by IRMA and bioassay (JCEM 42:958, 1976). To assess the pituitary stores of LH and FSH, after 8 h of spontaneous secretion we administered (2 h apart) 2 intravenous pulses containing 10 micrograms of a GnRH analog, and the sampling continued as described. Hormonal pulsatility was assessed by a computerized cluster analysis method (Am J Phys 250:E486, 1986) an by the multiple parameters deconvolution method (JCEM 66: 1291, 1988). In the infertile patients we found a significant diminution in the length and frequency of LH pulses, compared with the normospermic men. However, LH half life, the interpulse interval, the amplitude and the mass secreted per pulse rose in the infertile males compared with the controls. The increase in the LH half life suggests the secretion of a more acidic isoform of this hormone in the infertile group. After the GnRH injection the LH secreted mass and mean concentration rose significantly in both groups; this effect was higher in the infertile oligo-asthenozoospermic men. In this group we also found a decrease in the bioactive LH interpulse interval and therefore more pulses during the sampling interval, that produced a higher concentration of this kind of hormone in these patients. Oligo-asthenozoospermic men secreted approximately 70% more bioactive LH as a response to the first GnRH injection than the normal controls. The desensitization observed with immunoactive LH (diminution in the mass secreted after the second GnRH bolus compared with the first one) was also observed with bioactive LH. In the infertile men group we found a significant reduction in the FSH half life compared with the normospermic controls; this fact suggests that, contrarily to the results observed with LH, a more basic isoform is secreted in these patients.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1994

Inhibitory action of in vitro ethanol and acetaldehyde exposure on LHRH-and phorbol ester-stimulated testosterone secretion by rat testicular interstitial cells.

Ethanol and acetaldehyde have been shown to inhibit testicular steroidogenesis. However the mechanism(s) of signal transduction involved in their action is still unclear. We examined the possible involvement of phospholipid-sensitive, calcium-dependent protein kinase (protein Kinase C, PK-C) in the intracellular mechanism of action of ethanol and acetaldehyde by stimulating testosterone production in rat testicular interstitial cells with LHRH and the phorbol ester PDBu, both of which activate PK-C at receptor (LHRH) and post-receptor (PDBu) sites. Ethanol (2000 mg %) inhibited 10(-7) M LHRH and 200 nM PDBu-stimulated testosterone production by 81 +/- 4.7% and 60 +/- 20.4%, respectively. Acetaldehyde (20 mg %) reduced the amount of testosterone produced by 10(-7) M LHRH and 200 nM PDBu by 59.4 +/- 1.2% and 52.5 +/- 5.4% respectively. Basal testosterone levels were unaffected by ethanol and reduced by acetaldehyde. However, the functional test of cell viability by preincubating cells with these doses of ethanol and acetaldehyde did not decrease their ability to respond appropriately to subsequent stimulation with LHRH, demonstrating that cell viability was unaffected by incubation with these drugs. The data presented here suggest that direct ethanol and acetaldehyde exposure results in a reduced ability of the testicular interstitial cells to respond to stimulation of PK-C pathway.

Acetaldehyde↗
PubMed1977

Pituitary LH and FSH and testosterone secretion in infants with undescended testes.

Twelve male infants with undescended testes (5 bilaterally, 7 unilaterally) were studied between the ages of 1 week and 11 months. As in older pre-pubertal cryptorchid boys, a significant decrease of the LH response to LH-RH test was found, while basal plasma levels of gonadotrophins and FSH response to LH-RH were normal. Plasma testosterone levels were in the normal range, and Leydig cells responded to stimulation by HCG, the degree of this response being significantly and positively correlated to the LH peak elicited by LH-RH. It may be concluded that some early defect of the pituitary-Leydig cell axis is associated with undescended testis.

Chorionic Gonadotropin↗
PubMed1984

Influence of continuous gonadotropin-releasing hormone (GnRH) agonist treatment on luteinizing hormone and testosterone secretion, the response to GnRH, and the testicular response to human chorionic gonadotropin in male rhesus monkeys.

Five adult male rhesus monkeys were continuously infused for 56 days with 25 micrograms/day of GnRH agonist (Wy-40972; Ag) using an implanted osmotic pump. Bioassayable serum levels of LH were elevated 8-fold on the second day of Ag treatment and then declined precipitously to below pretreatment levels by day 15. Serum levels of testosterone (T) changed similarly during Ag treatment, except that the fall in serum LH levels preceded the decline in serum levels of T by at least 2 days. Ag administration also eliminated the diurnal variation in serum LH and T. GnRH administration (50 micrograms) induced a 13- to 20-fold rise in serum LH and a 3- to 7-fold increase in serum T in control monkeys. After 4 weeks of Ag administration , none of the animals responded to GnRH. Both control and experimental monkeys had a rise in serum T in response to hCG after 7 weeks of Ag treatment. Basal levels of LH and T returned to normal by 12 days posttreatment, and the serum LH and T responses to GnRH were normal 19 days posttreatment. These results indicate that 1) continuous administration of Ag is an effective method of inducing antiferility effects in male rhesus monkeys; 2) pituitary desensitization is a major factor involved in Ag-induced gonadal dysfunction in this species; and 3) the method of administration may be the critical factor in determining the effectiveness of GnRH agonists.

Animals↗