Testosterone

About: Testosterone is a research topic. Over the lifetime, 23258 publications have been published within this topic receiving 808079 citations. The topic is also known as: 4-androsten-17beta-ol-3-one & 4-Androsten-3-one-17b-ol.

Social suppression of reproduction in male naked mole-rats, Heterocephalus glaber.

Abstract: To investigate possible anatomical and endocrine differences between breeding and non-breeding male naked mole-rats, 113 animals from 24 captive and 4 wild colonies were studied. While breeding males had larger reproductive tract masses compared to non-breeders relative to body mass (P less than 0.01), spermatogenesis was active in all of the non-breeding males examined histologically (n = 9) and spermatozoa were present in the epididymides. Compared with non-breeders, breeding males had significantly higher urinary testosterone concentrations (mean +/- s.e.m.: 23.8 +/- 2.3 vs 5.2 +/- 1.4 ng/mg Cr respectively; P less than 0.001), and plasma LH (10.7 +/- 1.7 vs 5.0 +/- 0.8 mi.u./ml respectively; P less than 0.01). Single doses of 0.1, 0.5 or 1.0 microgram GnRH produced a significant rise in plasma LH concentrations 20 min after s.c. injection in breeding and non-breeding males at all doses (P less than 0.001). However, there were differences in the magnitude of the LH response following administration of GnRH between breeding and non-breeding males, with non-breeding males showing a dose-response and having lower plasma LH concentrations 20 min after a single injection of 0.1 or 0.5 microgram (P less than 0.05), but not 1.0 microgram, GnRH. This apparent lack of pituitary sensitivity of non-breeding males to single doses of exogenous GnRH was reversed by 4 consecutive injections of 0.5 microgram GnRH at hourly intervals, suggesting that the reduced sensitivity may be the result of insufficient priming of the pituitary by endogenous GnRH. These results indicate that, despite the fact that non-breeding males were apparently producing mature gametes, clear endocrine deficiencies existed in male naked mole-rats.

Increased activity of the hypothalamic-pituitary-testicular axis in infancy results in increased androgen action in premature boys.

Abstract: Context: Transient activation of the hypothalamic-pituitary-gonadal (HPG) axis is observed in boys during the first months of life. Previous research suggests increased HPG axis activation in premature infants, but the physiological significance of this has not been studied. Objective: The objective of this study was to evaluate the differences in reproductive hormone levels and their biological effects between full-term (FT) and preterm (PT) infant boys. Study Design and Participants: Twenty-five FT and 25 PT (gestational age 24.7–36.6 wk) boys were recruited at birth and followed up monthly from 1 wk to 6 months of age (d 7, months 1–6). Nineteen FT and 20 PT boys were reexamined at 14 months of age. Main Outcome Measures: Urinary gonadotropins and testosterone were measured in serial urine samples and compared with testicular and penile growth. Urinary prostate-specific antigen was measured as an androgen biomarker. Results: LH and testosterone levels were higher in PT boys (P < 0.001 for both) than FT...

Serum gonadotropin testosterone estradiol and estrone levels prior to and following bilateral vasectomy.

Abstract: Serum follicle stimulating hormone (FSH) luteinizing hormone (LH) estradiol (E2) estrone (E1) and testosterone (T) were determined prospectively in 41 men before and after bilateral vasectomy and in 41 simultaneous controls to evaluate whether vasectomy sex hormone levels. Radioimmunassays of the endocrine parameters were performed 3 times before and up to 24 months postvasectomy. Analysis of variance for repeated measures showed that there was no significant difference between the means of serum FSH LH T E2 and E1 concentrations measured in vasectomized men and those observed in controls. Whereas the means of the monthly serum T and E2 concentrations were unchanged through the entire 24-month study tiny but significant time-related alterations were noted for means of the monthly E1 FSH and E2 concentrations apparently caused by a minor drift in the assay procedure. Hence these results demonstrated the importance of simultaneous controls in long-term studies and call into question the validity of studies which report significant hormonal changes after vasectomy. These data indicate that vasectomy does not alter serum FSH LH T E2 or E1 levels and suggest that testicular function remains unchanged at least during the 1st 2 years of study.

Concentrations of steroids and gonadotropins in follicular fluid from normal heifers and heifers primed for superovulation.

Abstract: The concentrations of six steroids and of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) were measured in follicular fluid from preovulatory and large atretic follicles of normal Holstein heifers and from preovulatory follicles of heifers treated with a hormonal regimen that induces superovulation. Follicular fluid from preovulatory follicles of normal animals obtained prior to the LH surge contained extremely high concentrations of estradiol (1.1 +/- 0.06 micrograms/ml), with estrone concentrations about 20-fold less. Androstenedione was the predominant aromatizable androgen (278 +/- 44 ng/ml; testosterone = 150 +/- 39 ng/ml). Pregnenolone (40 +/- 3 ng/ml) was consistently higher than progesterone (25 +/- 3 ng/ml). In fluid obtained at 15 and 24 h after the onset of estrus, estradiol concentrations had declined 6- and 12-fold, respectively; androgen concentrations had decreased 10- to 20-fold; and progesterone concentrations were increased, whereas pregnenolone concentrations had declined. Concentrations of LH and FSH in these follicles were similar to plasma levels of these hormones before and after the gonadotropin surges. The most striking difference between mean steroid levels in large atretic follicles (greater than 1 cm in diameter) and preovulatory follicles obtained before the LH surge was that estradiol concentrations were about 150 times lower in atretic follicles. Atretic follicles also had much lower concentrations of LH and slightly lower concentrations of FSH than preovulatory follicles. Hormone concentrations in follicles obtained at 12 h after the onset of estrus from heifers primed for superovulation were similar to those observed in normal preovulatory follicles at estrus + 15 h, except that estrogen concentrations were about 6-40 times lower and there was more variability among animals for both steroid and gonadotropin concentrations. Variability in the concentrations of reproductive hormones in fluid from heifers primed for superovulation suggests that the variations in numbers of normal embryos obtained with this treatment may be due, at least in part, to abnormal follicular steroidogenesis.