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PubMed2001

Lesion of the insular cortex affects luteinizing hormone and testosterone secretion of rat. Lateralized effect.

The possible involvement of the insular cortex in the neural control of the hypophyseal-testicular axis was studied in male rats. Right- but not left-sided lesion of the insular cortex resulted in a significant decrease in basal testosterone secretion in vitro and serum testosterone concentration. Both right- and left-sided lesions of the insular cortex induced significant increase in serum luteinizing hormone (LH) concentration. Unilateral lesion of the insular cortex on either sides had no effect on serum follicle stimulating hormone (FSH) level. The results indicate that the insular cortex is involved in the control of testosterone and LH secretion. The data further suggest that the right insular cortex plays a predominant role in the control of male endocrine reproductive processes.

Animals↗
PubMed1989

Dynamics of testosterone secretion by the rat testis: implications for measurement of the intratesticular levels of testosterone.

Testosterone concentrations have been measured in testicular interstitial fluid (IF), and in blood plasma sampled from various parts of the rat testis and spermatic cord, to assess (1) the most accurate method for determination of the intratesticular levels of testosterone, and (2) the route of secretion of testosterone from the testis. In untreated adult rats, testosterone concentrations were highest in blood collected from veins on the surface of the testis (269.50 +/- 30.63 (S.E.M.) nmol/l), but were reduced by 56% on average in blood collected from veins at the proximal end of the spermatic cord (123.06 +/- 24.75 nmol/l), and were reduced considerably in peripheral venous blood (4.55 +/- 0.55 nmol/l). Similar changes occurred in adult rats in which steroidogenesis was either stimulated (by treatment with human chorionic gonadotrophin; hCG) or inhibited (by treatment with aminoglutethimide; AMG), and in rats of various ages during sexual maturation. The reduction in testosterone levels during passage of blood from the testis up the spermatic cord is probably due mainly to dilution by incoming arterial blood which transfers to venous blood via anastomoses in the spermatic cord. Venous-arterial transfer of testosterone in the cord contributed to this in only a minor way. Concentrations of testosterone in testicular IF were always greater than testicular venous concentrations in control, developing and hCG-stimulated rats, but were comparable in rats treated with AMG to suppress Leydig cell steroidogenesis. These and other results demonstrate that the method of drip-collection of IF results in over-estimation of the actual intratesticular levels of testosterone.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Neonatal hemiorchidectomy of bulls alters plasma growth hormone levels and advances onset of pubertal testosterone secretion.

Bovine GH and testosterone profiles were determined in plasma collected at 20 min intervals during 3 hr bleeding periods on day 25 of life and every 15 days thereafter in six intact (I) Holstein bull calves and in six others which had been hemiorchidectomized (HO) at 10 days of age. In I bulls average plasma GH concentrations varied between 7.9 and 14.5 ng/ml (P greater than 0.05) until 130 days of age, after which the GH level gradually rose (P = 0.007) to a maximum of 19.4 ng/ml on day 205 of life. Episodic release of GH was apparent in 55 day-old and older I bulls and in HO bulls of all ages. Plasma GH concentrations in HO bulls were higher than in I bulls 15 and 30 days after surgery (P = 0.07), at which times the levels in HO bulls averaged 19.6 and 22.5 ng/ml and in I bulls 10.3 and 10.2 ng/ml, respectively. Plasma GH in HO bulls again exceeded that of I bulls at ages of 130-190 days (P = 0.04). Plasma testosterone was virtually nondetectable before 130 days of age in I bulls but thereafter exhibited the typical episodic pattern. In HO bulls, plasma testosterone concentrations began to rise 15 to 30 days before those in I bulls, resulting in an age X treatment interaction (P less than 0.0001). Furthermore, average testosterone levels were higher (P = 0.07) in HO than I bulls at 235 and 250 days of age.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

[A study on testosterone secretion in neonates].

Serum testosterone (T) concentrations in 106 umbilical venous bloods and 104 neonatal venous bloods, which were obtained from preterm (32-36w) and term (36-41w) infants, were measured by RIA. Cord T levels of boys were higher in preterm infants than in term infants, and those of preterm infants were higher in boys than in girls. Neonatal T levels of girls decreased following delivery. But those of boys increased after 10 days of life. T levels were higher in boys than in girls at 11-30 days of life. Differences between preterm and term infants were not significant.

Female↗
PubMed1984

Post-weaning differential housing and testosterone secretion in male mice.

The effect of different densities of animals per cage on basal testosterone secretion and its response to some stimuli was studied in prepuberal male mice. Mice housed with 110 or 55 cm2 of floor space per animal showed the same basal serum testosterone and hCG-induced testosterone release. Likewise, in a second experiment, the same basal serum testosterone and a similar response to acute noise stress were found in mice housed at 132, 66 or 22 cm2 of floor space per animal. These results suggest that post-weaning crowding did not affect Leydig cell function in male mice.

Adrenal Glands↗
PubMed1987

Short term administration of gonadotropin-releasing hormone analog to a patient with a testosterone-secreting ovarian tumor.

A GnRH superagonist, buserelin, was administered for 16 days to a postmenopausal woman with a testosterone-secreting ovarian tumor. Serum gonadotropin levels decreased by more than 70%, and serum testosterone fell by more than 50%. This short term study demonstrates that in these uncommon tumors androgen secretion is gonadotropin sensitive, and suggests that GnRH analogs may have therapeutic value in such patients.

Administration, Intranasal↗
PubMed1992

Restraint inhibits luteinizing hormone and testosterone secretion in intact male rhesus macaques: effects of concurrent naloxone administration.

The present study investigates how restraint affects the hypothalamo-hypophysial adreno-cortical axis and the hypothalamo-hypophysial gonadal axis in intact, adult male rhesus macaques. Restraint was chosen because it is not physically painful or harmful to the animal, but rather serves both as a physical and psychological stressor. Blood samples were collected from a remote site at 15-min intervals beginning at 07.00 h from tethered adult male rhesus macaques. Each of 4 animals was subjected to 6 h of chair restraint after a 3-hour control period in the animals' home cage. Samples were collected for an additional 6 h at the end of the restraint period when the animal was returned to its home cage. Brief anesthesia with ketamine (administered through the indwelling catheter) facilitated transfer of the animals to and from the chair. Blood samples were collected from 4 undisturbed males to document LH and testosterone secretion throughout the day. Plasma ACTH and cortisol, measured as indexes of stress, were elevated within 15 min after initiation of restraint and remained elevated for most of the restraint period. Conversely, LH and testosterone began to fall immediately after restraint and remained suppressed for several hours after the animals were removed from restraint and returned to their home cage. Testosterone levels were more consistently inhibited than were LH levels, a reflection of the fact that in some animals, testosterone remained low after the return of pulsatile LH secretion. In studies with naloxone (Nx), the opiate receptor antagonist (5 mg bolus plus 5 mg/h) was given beginning either at the initiation of restraint (n = 2) or 2 h thereafter (n = 2), and continued until the end of the restraint period. With Nx treatment of the restrained animals, both ACTH and cortisol were elevated as in the controls and LH and testosterone secretion were significantly increased within 1-2 h. However, after the Nx treatment was terminated and the animals were returned to their home cages, plasma levels of LH and testosterone were not different from levels in restrained animals and were significantly less than levels in untreated animals. These data show that restraint is a potent stimulus for activation of the HPAC axis and inhibits both LH and testosterone release. The pathway through which restraint inhibits LH release probably includes endogenous opiate suppression of hypothalamic GnRH release since Nx partially blocks the effect of stress.

Adrenocorticotropic Hormone↗
PubMedDate not supplied

[Effect of blockade of opiate receptors by naloxone on lutropin (LH), follitropin (FSH) and testosterone secretion in patients after kidney transplantation].

The influence of opioid receptors blockade by naloxone on lutropin (LH), follitropin (FSH) and testosterone secretion induced by LH-RH was assessed in 12 male kidney transplant patients with stable graft function (KTP) treated by cyclosporine A and prednisone and in 15 healthy subjects. In KTP normal plasma levels of LH in spite of significantly reduced testosteronemia and a reduced response of LH to LH-RH was observed. After blockade of opioid receptors by naloxone normalization of the response of LH secretion to LH-RH was found and a higher increase of the plasma testosterone level was observed in KTP than in healthy subjects. Results obtained in this study suggest abnormal functioning of the hypothalamic-pituitary--gonadal axis in KTP and participation of opioid receptors in its pathogenesis.

Adult↗
PubMedDate not supplied

[Testosterone secretion and the gonadotropic function of the pituitary gland under condition of limited food intake].

Experimental data on testosterone secretion and gonadotropic function of the hypophysis and their changes under conditions of a limited nutritional ration are presented. Experimental rabbits proved to display a sharp fall of testosterone in the blood flowing from the testes and a rise of gonadotropic hormones in the hypophysis. The mentioned fact should be taken into consideration when the nutritional ration is diminished for experimental purpose or under clinical conditions on certain indications connected with the necessity of decreasing the caloric value and the quantity of food consumption.

Animals↗
PubMed1983

Testosterone-secreting adrenal ganglioneuroma containing Leydig cells.

A 58-year-old woman was virilized by a testosterone-secreting adrenal ganglioneuroma containing Leydig cells with crystalloids of Reinke. Examination of the ovaries revealed stromal hyperthecosis and hilus cell hyperplasia. The evidence from this case, as well as related cases in the literature, suggests that cells of the adrenal gland may become transformed into cells of gonadal type in both hyperplastic and neoplastic disorders.

Adrenal Gland Neoplasms↗
PubMed1999

Managing a patient with presumed testosterone-secreting ovarian tumor.

We report the case of a 70-year-old woman who was presumed to have right ovarian testosterone-secreting tumor and was treated with long-acting gonadotropin-releasing hormone agonist therapy plus add-back hormone replacement therapy. The patient presented with various medical problems including hypertension, intracranial hemorrhage, myocardial infarction, unstable angina pectoris, and poor control of diabetic mellitus and had exhibited rapid symptoms of androgen excess such as progressive hirsutism and bilateral temporal balding for half a year. Tumor survey was negative except for an elevated testosterone level. Renal vein catheterization successfully detected a right ovarian androgen-secreting tumor. Because the patient was deemed medically unable to tolerate surgery, she received an alternative treatment consisting of 6 months of gonadotropin-releasing hormone-agonist (GnRH-a) and add-back hormone replacement therapy (HRT). Serum testosterone levels returned to normal limits after administration of the first dose of GnRH-a. A follow-up tumor survey was negative. The patient has been alive and free of disease for 8 months after six doses of GnRH-a. We conclude that this strategy might be used as urgent therapy in a medically compromised patient with presumed ovarian androgen-secreting tumor.

Aged↗
PubMed1996

Characteristics of luteinizing hormone (LH) and testosterone secretion, pituitary responses to LH-releasing hormone (LHRH), and reproductive function in young bulls receiving the LHRH agonist deslorelin: effect of castration on LH responses to LHRH.

Young bulls were treated with graded dosages of the LHRH agonist deslorelin to ascertain 1) whether increased testosterone secretion persisted over a wide dose range of agonist; 2) whether elevated testosterone was maintained long-term and, if so, what effects there were on reproductive function; and 3) what pituitary responses to exogenous LHRH occurred in intact and castrated bulls receiving deslorelin. In three experiments, bulls received dosages of agonist ranging from approximately 0.15 to 29.0 micrograms deslorelin/kg live weight/day, by means of either bioimplants or injections. At all dosages, deslorelin induced an acute increase in plasma LH concentrations that declined after 24 h but remained at greater concentrations than in controls, although the differences were relatively small. Profiles of LH in bulls treated with deslorelin were characterized by tonic secretion with no clear evidence of LH pulses. Plasma testosterone concentrations were increased at all dosages of deslorelin and in one experiment remained greater than in controls for over 100 days of treatment. This increase was associated with an increase in the rate of testis growth; however, there were no apparent improvements in semen parameters. Bulls receiving deslorelin did not show a typical postcastration rise in plasma LH concentrations, and neither intact nor castrated bulls receiving deslorelin showed an increase in plasma LH after injection of natural sequence LHRH. The absence of endogenous LH pulses and lack of response to exogenous LHRH suggested that the anterior pituitary in bulls receiving LHRH agonist becomes desensitized. However, LH secretion persisted in a tonic manner and was associated with elevated plasma testosterone concentrations. The failure of both intact and castrated bulls receiving deslorelin to respond to exogenous LHRH suggested direct effects of deslorelin on the pituitary, rather than an interaction with steroid feedback.

Animals↗
PubMed1981

Acetaldehyde acutely impairs canine testicular testosterone secretion.

Utilizing a method for perfusion of the in vivo isolated canine testis we have examined basal and human chorionic gonadotropin (hGC)-stimulated testosterone production of testes acutely exposed to ethanol and acetaldehyde. Ethanol infused at concentrations of 0.2 g/dl to 0.6 g/dl did not alter basal of hCG-stimulated testicular testosterone production of one testis when compared to the saline-infused control testis of the same animal. However, acetaldehyde infused at a concentration of 0.2 mg/dkl, a level similar to that found in humans drinking moderate amounts of ethanol, significantly impaired hCG-stimulated testicular testosterone production. It is concluded that acetaldehyde acutely impairs hCG-stimulated testicular testosterone secretion by a direct effect on the testis, but ethanol does not.

Acetaldehyde↗
PubMed1982

Luteinizing hormone and testosterone secretion in young and old male mice.

This study documents, for the first time, the temporal pattern of luteinizing hormone (LH) release and the relationship between plasma LH concentrations and testicular androgenic responses in young and aged male mice. Both LH and testosterone were measured in the same samples of blood plasma withdrawn at frequent intervals over 9 h from awake, mobile mice through intra-atrial cannulae. The results demonstrate unequivocally that LH and testosterone are discharged into the circulation in discontinuous pulses in this important animal model. Robust episodes of LH release occur at infrequent intervals and increments of circulating LH occasion time-delayed elevations of plasma testosterone. Thus, the frequency of LH release is the major factor determining peripheral concentrations of this gonadotropins. The obvious one-to-one coupling between intermittent LH discharges and testosterone secretion has significant functional and investigative implications. The reduction in circulating testosterone concentrations observed in old male mice is a consequence of fewer LH discharges, which is due most likely to the slowing of a neural GnRH pulse generator. However, age-related declines in copulatory behavior were not associated with altered patterns of hormone secretion. Hence, we suggest that deficits in sexual behavior and episodic LH release in old males result from neural senescence rather than diminished testicular support of reproduction.

Aging↗
PubMed1991

Testosterone-secreting virilizing adrenal adenoma with human chorionic gonadotrophin receptors and 21-hydroxylase deficiency.

A 60-year-old woman was evaluated for persistently elevated serum testosterone concentrations after bilateral ovariectomy. Her serum cortisol, androstenedione, dehydroepiandrosterone sulphate and 17-hydroxyprogesterone levels were normal, and decreased after dexamethasone administration. Those of testosterone (17.8-18.4 nmol/l) were remarkably high (normal range 0.7-2.8 nmol/l), were not suppressed by dexamethasone, but clearly increased after hCG administration (up to 128 nmol/l). Computed tomography revealed an adenoma in the right adrenal gland and adrenal scintigraphy under dexamethasone suppression visualized this adenoma. A right adrenalectomy was performed. (1) The tumour was histologically and ultrastructurally adrenocortical adenoma of zona reticularis cell type. (2) The adenoma tissue contained hCG receptors (198 fmol/g). (3) During tissue culture both ACTH and hCG were capable of maintaining its testosterone production, which was attenuated with time without stimulation. (4) The adenoma tissue did not elaborate 21-hydroxylated steroids in contrast to normal adrenal tissue. Thus the aberrant endocrine behaviour of this gonadotrophin-responsive testosterone-secreting adenoma of adrenal zona reticularis cell origin can be explained by ectopic functional hCG receptors and the lack of 21-hydroxylase activity.

Adenoma↗
PubMed1995

Effects of growth hormone and insulin-like growth factor I on testosterone secretion in premature male rats.

Present study was planned to clarify the effects of GH and insulin-like growth factor I (IGF-I) on testosterone secretion using premature male rats. Forty rats were divided four groups. GH, IGF-I, both of them or normal saline solution as control were subcutaneously administered to the rats of each group for seven days from 3-week to 4-week of age. After the treatment, six of each group were used to human chorionic gonadotropin (hCG) loading and four to Leydig cell preparation. Serum testosterone responses to hCG loading were significantly higher in 4-week-old rats treated with GH and/or IGF-I for 1 week than in control rats. However, the responses were similar among three treated groups (GH, IGF-I and both). After one-week treatment with GH and/or IGF-I, isolated Leydig cells were prepared from testes of 4-week-old rats and testosterone production by the stimulation of hCG was examined. Amounts of testosterone production stimulated by hCG were significantly greater in the treated rats than in control rats. These findings suggest that GH mediated by IGF-I promotes the testicular responsiveness to gonadotropin on testosterone production in premature rats.

Analysis of Variance↗