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PubMedDate not supplied

Spontaneous growth hormone and somatomedin-C/insulin-like growth factor-I secretion in obese subjects during puberty.

It has been reported that adult obese subjects present a reduced growth hormone secretion. As no data are available in the pubertal period, which is characterized in lean subjects by an increased spontaneous growth hormone secretion, the growth hormone circadian concentration was studied in a group of 18 obese male subjects in different pubertal stages, and compared to 26 age-matched control subjects. The data observed evidenced no statistically relevant differences regarding LH and FSH circadian secretion and morning testosterone concentration. On the contrary a statistically significant (p less than 0.02) difference in growth hormone 24 h integrated concentration was evident, particularly in prepubertal subjects; the sleep-related peak was evident in 28% of obese subjects and in 85% of controls. Sm-C/IGF-I concentration was similar to the concentration observed in controls in the prepubertal stage, but did not show the expected increase in the late puberty. Auxological data, performed on a sample of 80 subjects, showed both advanced height and bone age at beginning of puberty, and a trend toward a reduction of percentile for height in parallel with the pubertal maturation, suggesting that pubertal growth spurt in obese subjects is at least less pronounced than in lean subjects. It is concluded that GH and Sm-C/IGF-I secretion is impaired during puberty in obese subjects, leading to a reduced growth rate, while in the prepubertal period factors other than GH may replace or even potentiate its action.

Adolescent↗
PubMed1997

The effect of the aromatase inhibitor fadrozole and two polynuclear aromatic hydrocarbons on sex steroid secretion by ovarian follicles of coho salmon.

A variety of endogenous and exogenous factors can influence sex steroid production by salmon ovarian follicles and ultimately impact reproductive development. We examined the effect of an aromatase inhibitor, fadrozole, and common environmental contaminants (PAHs) on sex steroid secretion by ovarian follicles. Ovarian follicles of coho salmon were incubated in vitro with various concentrations of testosterone (0.10-0.40 microM) and fadrozole (10 and 100 microM), or with varying doses (between 0.05 and 5.0 microM) of the PAHs beta-naphthoflavone (BNF) and 20-methylcholanthrene (20-MC). 17 beta-Estradiol secretion was significantly reduced when follicles were incubated in the presence of fadrozole, BNF, or 20-MC. In contrast, 17 beta-estradiol production by ovarian follicles increased in a dose-dependent manner when incubated with increasing doses of the aromatizable androgen testosterone. Although increasing doses of PAHs significantly reduced follicular 17 beta-estradiol production no effect on testosterone secretion was observed. Hence, both fadrozole and PAHs can significantly reduce 17 beta-estradiol secretion by salmon ovarian follicles and may affect female sexual development.

Animals↗
PubMed1991

Possible involvement of hypothalamic monoamines in mediating the action of alpha-2u-globulin on the pituitary-testicular axis in rats.

A major androgen-dependent urinary protein of male rodents, alpha 2u-globulin, has been shown to influence adenohypophyseal hormone release. In an attempt to elucidate the mechanisms of its action, we have examined several parameters of hypothalamic and pituitary function in adult male rats treated for 2 weeks with two injections daily of 0.75 mg alpha 2u-globulin and sacrificed 16 h after the last injection. This treatment led to an increase in plasma luteinizing hormone levels, a decrease in plasma prolactin levels, an increase in testosterone concentrations in both plasma and testicular tissue, and increases in testicular weights. The norepinephrine turnover in median eminence and anterior hypothalamus was increased in alpha 2u-globulin-injected animals, while the norepinephrine turnover in the remaining medial basal hypothalamus was reduced. alpha 2u-Globulin-treated animals had a significantly decreased dopamine turnover in the anterior hypothalamus, while in the medial basal hypothalamus the dopamine metabolism was increased. These data suggest that alpha 2u-globulin-induced changes in gonadotropin and prolactin secretion are mediated by changes in catecholamine metabolism in several hypothalamic regions. Increased testosterone secretion appears to be due to increased secretion of gonadotropins from the pituitary.

Alpha-Globulins↗
PubMed2000

Age-dependent effect of Freund's adjuvant on 24-hour rhythms in plasma prolactin, growth hormone, thyrotropin, insulin, follicle-stimulating hormone, luteinizing hormone and testosterone in rats.

The effect of Freund's adjuvant administration on 24-hour changes of plasma prolactin, growth hormone (GH), thyrotropin (TSH), insulin, follicle-stimulating hormone (FSH), luteinizing hormone (LH) and testosterone were studied in young (2 months) and aged (18 months) male Wistar rats. Rats were injected s.c. with Freund's adjuvant or adjuvant's vehicle and, 18 days later, they were killed at 6 different time intervals throughout a 24-hour cycle to measure circulating hormone levels by specific RIAs. Young rats receiving adjuvant's vehicle exhibited significant time-of-day-dependent variations in plasma TSH, LH and testosterone, with maximal levels at 1300 h, 0100 h and 1700 h, respectively. Prolactin and insulin levels, analyzed globally in a factorial ANOVA, showed significant time-of-day changes with maximal levels at 1300 - 1700 h and 2100 h, respectively. The daily rhythms in plasma LH and testosterone found in young rats were not longer observed in Freund's adjuvant-injected rats, while as far as TSH, a second peak was observed at 0100 h after Freund's adjuvant administration. Twenty-four hour rhythms in circulating TSH, LH and testosterone were blunted in old rats receiving either Freund's adjuvant or its vehicle. Aged rats exhibited significantly higher circulating levels of prolactin, and lower levels of GH, TSH, FSH and testosterone. The results indicate that secretion of prolactin, GH, TSH, FSH and testosterone are age-dependent, as are the responses of TSH, LH and testosterone to Freund's adjuvant administration.

Aging↗
PubMed1979

Origin of estrogen in normal men and in women with testicular feminization.

The purpose of this study was to quantify the various sources of estrone (E1) and 17 beta-estradiol (E2) production in normal men and in women with testicular feminization. The mean production rate of E1 in four young adult men was 58 micrograms/24 h, while that of E2 was 44 micrograms/24 h. In these men, E1 production could be accounted for totally by extraglandular formation through 1) aromatization of plasma androstenedione, 2) conversion of E2 which was formed from the aromatization of plasma testosterone, and 3) conversion of secreted E2. In these men, only 12 micrograms or less of E2 production could not be accounted for by extraglandular formation from plasma C19 precursors, and is presumed to have arisen by testicular secretion. In six women with testicular feminization, the mean production rate of E1 was 99 micrograms/24 h, while that of E2 was 77 micrograms/24 h. THe amount of E2 production that arose by glandular secretion could be computed in four of these women and was considerably greater than that found in the young adult men. In these women with testicular feminization, an average of 44 micrograms/24 h E2 could not be accounted for by extraglandular formation and is presumed to have arisen by testicular secretion. The mean plasma production rate of testosterone in the normal men was 5.7 mg/24 h, while that in the women with testicular feminization was 8.3 mg/24 h. However, the range of plasma production rates of testosterone in the women with testicular feminization was large (1.3--17.0 mg/24 h).

Adolescent↗
PubMed2006

Changes in endocrine profile and reproductive organs during puberty in the male marmoset monkey (Callithrix jacchus).

Data on pubertal maturation in male marmoset, a model for human reproduction, are scant and conflicting. We collected data on novel parameters to characterize puberty. Twenty-five marmoset monkeys were assigned to five age groups by weeks (wk): 21 (pre-pubertal), 43 (onset of puberty), 52 (fully pubertal), 70 (mature), and 116 (fully adult). Serum and intratesticular testosterone and pituitary bioactive chorionic gonadotropin (bioCG) were measured. Testicular development was assessed by ultrasonography, histology, and flow cytometry. Three consecutive blood samples revealed extreme fluctuations in testosterone concentrations, suggesting an erratic secretion. Age-related changes in serum testosterone and pituitary bioCG concentrations were observed. Intratesticular androgens (ITAs) showed high fluctuations within groups at all ages and were high in some animals by 21 wk. Unexpectedly, no correlation between pituitary bioCG and serum testosterone or ITAs was found, but these parameters significantly correlated with testicular weight and volume. These observations were consistent a dependence on the testis growth on bioCG. Unfortunately, the low serum levels of bioCG were not measurable in this study. At 43 wk, the animals reached puberty. At 52 wk of age, animals attained maximum body and epididymal weights and qualitatively normal spermatogenesis, but testes continued growing, reaching a maximum of all parameters at 70 wk of age, without further major changes at the age of 116 wk. It is concluded that (1) gonadal activation is evident at wk 21, (2) the male marmoset reaches the pubertal threshold around 43 wk of age, attains qualitative parameters at 52 wk, matures further to sexual maturity at 70 wk, and (3) serum testosterone and ITAs are highly variable without any identifiable correlation with pituitary bioCG.

Animals↗
PubMed1979

The effects of long-term administration of either a crude inhibin preparation or an antiserum to FSH on serum hormone levels, testicular function and fertility of adult male rats.

Adult male rats were given either daily injections of ram rete testis fluid for periods of up to 70 days or injections of an antiserum against FSH every 3 days for 90 days. Compared with the control groups, the rats injected with ram rete testis fluid had lowered serum FSH levels, but only at treatment periods of 30 days and less. The levels of LH and testosterone in serum, testicular fluid secretion, sperm counts, testis weights and fertility were not affected by rete testis fluid treatment. The rats injected with anti-FSH serum exhibited an impairment of fertility which was never complete and evident only after 49 days of treatment. After 90 days of anti-FSH treatment, testis weight and free serum FSH were reduced, but sperm counts, testicular fluid secretion and serum levels of LH and testosterone were not affected.

Animals↗
PubMed1980

Hypothalamic, pituitary, testicular, and secondary organ functions and interactions during the sexual maturation of the male rat.

Puberty in the male rat is a complex process that involves maturational changes in the hypothalamus, pituitary, testes, and secondary sexual organs and in their interrelationships. During the course of sexual maturation the negative feedback control systems for the gonadotropins become less responsive to testosterone while the testes become more responsive to LH. In the immature rat testosterone can potentiate the effect of LH--RH on pituitary LH release; this response is lost with sexual maturation. LH--RH sensitizes the mature male pituitary glands for subsequent LH--RH administration; this self-priming effect is not present in the immature rat. The responsiveness of the secondary organs to testosterone is also altered with age, as is the relative proportion of testosterone and androstendione secreted by the testes. Experiments designed to prevent or mimic the transition in testicular steroid secretion suggest that it may be a critical component of sexual maturation in the male rat. An elevation in androstendione appears to be capable of delaying the maturation of the LH negative feedback system, the prostate gland, and the LH--RH self-priming effect.

Androstenedione↗
PubMed1981

Is ethanol a testicular toxin?

A method is described by which the testis of the rat can be isolated and selectively perfused in vitro to examine the effect of potential gonadal toxins. Using this system, the effect of ethanol at levels commonly found in the plasma of nonalcoholic men who drink alcohol was evaluated. Ethanol was found to significantly reduce (p less than 0.01) testosterone production and secretion by the isolated perfused testis. The advantage of such a system is that it permits examination of the effect of specific testicular toxins, such as alcohol, independent of hepatic metabolism and/or hypothalamic-pituitary suppression by such substances. These results suggest that ethanol, independent of hepatic metabolism and/or hypothalamic-pituitary suppression, is a direct testicular toxin.

Animals↗
PubMed1997

Chloroquine therapy reduces oestrogen production in females.

In this study: it has been shown that chloroquine therapy reduces both testosterone and oestradiol secretion in females. This reduction was marked the longer the duration of exposure to the drug. The animals did not regain the pretreatment sex hormone levels even after they were left for one month to recover without chloroquine intake. It seems that the inhibitory effect of chloroquine is mediated through the production of epidermal growth factor (EGF). This latter exerts an inhibitory effect on the LH Lutenzing hormone receptors in ovarian granulosa cells. EGF has also got a suppressive effect on 17 a-hydroxylase enzyme; a key enzyme which is necessary for the hydroxylation of pregnenolone and progesterone in the ovary Hydroxy pregnenolone is a precursor of androstendione, while 17 a-hydroxyprogesterone is a precursor of testosterone. Both androgens (androstendione and testosterone) are aromatized to oestrogens in the gonadal and extragonadal tissues. This study draws the attention to prolonged chloroquine therapy in collagen disorders. In such diseases as the drug is used on long term basis, it should be used with utmost care specially in old female patients who are already candidates for oestrogen hormonal replacement therapy to protect their fragile status.

Animals↗
PubMed1996

[Search for biochemical factors implicated in the pathogenesis of alcoholism in different ethnic populations].

A Chukotka indigenous population (the Chukchis, Eskimos) craving alcohol was examined. Changes in the levels of endogenous ethanol (EE) and its relation to calcium homeostasis, hypophyseal-adrenocortical hormones (stress) in the body are regarded as a possible role in alcohol motivation and ethanol dependence. The frequency and pattern of alcohol consumption, high alcoholism incidence rates in the family history may consider the Arctic Mongoloids as a group at high risk for alcoholism. Manifestations, such as lost control over the dose used, alcoholic amnesia, occasional use of alcohol poisoning doses with high rates of alcohol dependence, withdrawal syndrome, were noted in more than half the examines. The reproduction accuracy of correlations between the baseline signs was maximizing by factorial analysis. Four major factors (63.3% of complete variability) were singled out, two aspects were found in the system of metabolism and biochemical variabilities: 1) the secretion of cortisol, testosterone and the activity of 2-hydroxybutyrate dehydrogenase (HBDH) contributes to the increase of EE concentrations with the simultaneous decrease in the blood levels of ionized calcium (Ca++) and uric acid (UA). On the contrary, higher Ca++ and UA concentrations directly or indirectly inhibit hormones and the functional activity of the adrenal cortex, testes and lower the levels of EE, some enzymes, and total protein, 2) Calcitonin (CT) and parathyroid hormone (PTH) seem to be factors favouring the activation of insulin that enhances the membranous transport not only of glucose, but some other saccharides together with EE. The findings suggests that there is an intricate impact of balance ratios in the scheme wherein Ca++ is likely to act as a link between the stimulus and secretion of hypophyseal, adrenal, thyroid, parathyroid hormones, on the one hand, and EE concentrations. A relationship of pleiads reflects a common process of the integration of neurohumoral mechanisms and the regulation of calcium metabolism. The findings serve as a basis for further studies of different links of the pathogenetic mechanisms responsible for the development of alcoholism in terms of ethnic features.

Adult↗
PubMed1976

Effect of alpha-melanocyte-stimulating hormone and testosterone on cutaneous and modified sebaceous glands in the rat.

The effects of alpha-MSH and testosterone propionate on sebum secretion, sebaceous gland volume, dermal lipogenesis, and preputial gland weight and lipogenesis were examined in hypophysectomized rats. Hypophysectomy reduced sebum secretion, sebaceous and preputial gland size, and dermal and preputial gland lipogenesis. The greatest effects were seen on the biosynthesis of wax esters and squalene. Testosterone propionate (TP) increased sebum secretion, sebaceous gland volume and preputial gland weight and lipogenic activity, but had no significant effect on the pattern of lipid labelling. alpha-MSH had no effect on sebaceous or preputial gland size, but increased sebum secretion and dermal lipogenesis, especially wax ester biosynthesis. When given together TP and alpha-MSH had a synergistic effect on sebum secretion and on dermal and preputial gland lipogenesis, and the pattern of lipid labelling was shifted towards normal. TP and alpha-MSH also showed synergism in increasing preputial gland weight, but together they had no greater effect on sebaceous gland volume than that achieved with TP alone. These results suggest that TP and alpha-MSH have different actions on the sebaceous glands with alpha-MSH acting predominantly on lipogenesis and TP on cellualr proliferation and turnover leading to an increase in gland size. Preputial glands differ from cutaneous sebaceous glands in their response to alpha-MSH and androgen which could be a reflection of their more specilized function.

Animals↗
PubMed1983

Circannual rhythms of plasma luteinizing hormone, follicle-stimulating hormone, testosterone, prolactin and cortisol in prepuberty.

For a period of four years we have been studying 106 healthy males and 66 healthy females, aged 6-10, by cross-sectional design, to look for evidence of a circannual rhythm in LH, FSH, testosterone, PRL, and cortisol secretion. Plasma samples were taken at 0800 h and all hormones were measured by RIA. A cosine function was fitted to the single data to indicate any significant circannual (about 1 year) rhythm and to estimate its parameters: mesor, amplitude, and acrophase. Annual changes were validated in the secretion of: LH (annual crest time in January in both sexes), testosterone (studied only in males, annual crest time in July), and PRL (significant rhythm only in females with annual crest time in March). FSH and cortisol did not show an annual rhythm in both sexes. Our data suggest that sex influences the circannual hormonal rhythms from prepuberty onwards.

Activity Cycles↗
PubMed1985

Peripheral androgen levels in the male brush-tail possum (Trichosurus vulpecula).

Radioimmunoassays were established for the measurement of total androgens and the specific measurement of testosterone and 5 alpha-dihydrotestosterone in peripheral plasma of the brush-tail possum. Androgen concentrations were measured in blood collected from indwelling jugular cannulae to determine whether the normal pattern of androgen secretion in this species was episodic and to attempt to relate total androgen and the pattern of testosterone secretion to the changes previously reported in prostatic, but not epididymal, weight in the breeding season. Blood was collected from restrained animals at varying time-intervals during daylight hours and darkness. Despite an apparent good adaptation to the sampling procedure there was generally a progressive decline in plasma androgen level during the collection period. This was true for animals bled during or out of the breeding season. There was no significant seasonal effect on the androgen concentration in the initial blood sample. When less restraint was used, two of three animals showed fluctuations in androgen levels over the 7-h sampling period. Testosterone levels in blood obtained by cardiac puncture were four- to nine-fold higher than those of 5 alpha-dihydrotestosterone but levels of these androgens in samples obtained during the breeding season were not significantly different from those obtained out of season. The results do not argue for a pulsatile release of testosterone in the possum but do demonstrate a marked capacity for changes in the peripheral androgen concentration. There was a poor correlation between testosterone and 5 alpha-dihydrotestostosterone levels and prostatic weight.

Androgens↗
PubMed2000

Serum concentrations of luteinizing hormone, growth hormone, testosterone, estradiol, and leptin in boars treated with n-methyl-D,L-aspartate.

Three experiments were conducted to determine the effects of n-methyl-D,L-aspartate (NMA), an agonist of the excitatory amino acid glutamate, on secretion of hormones in boars. In Exp. 1, boars (185.0+/-.3 d of age; mean +/- SE) received i.v. injections of either 0, 1.25, 2.5, 5, or 10 mg of NMA/kg BW. There were no effects of NMA (P>.1) on secretion of LH and testosterone. Treatment with NMA, however, increased (P<.01) circulating GH concentrations in a dose-dependent manner. In Exp. 2, boars (401 d of age) received an i.v. challenge of NMA at a dose of 10 mg/kg BW or .9% saline. Treatment with NMA, but not saline (P>.1), increased serum concentrations of LH (P<.01), GH (P <.01), and testosterone (P<.06). In Exp. 3, boars that were 152, 221, or 336 d of age were treated i.v. with NMA (10 mg/kg BW). Across ages, treatment with NMA increased circulating concentrations of LH (P<.07) and testosterone (P<.01). However, NMA increased (P<.01) mean GH concentrations in only the oldest boars. Treatment with NMA had no effect (P>.1) on circulating concentrations of estradiol or leptin; however, estradiol concentrations increased (P<.03) with age. In summary, NMA increased secretion of LH, GH, and testosterone in boars. However, endocrine responses to treatment with NMA may be influenced by age of the animal. Finally, NMA did not influence circulating concentrations of estradiol or leptin.

Age Factors↗
PubMed1978

Primary amenorrhea associated with hirsutism, acanthosis nigricans, dermoid cysts of the ovaries and a new type of insulin resistance.

We describe a 15 1/2 year old presenting with primary amenorrhea, hirsutism, acanthosis nigricans and insulin resistance. Ovarian vein catheterization studies revealed bilateral excess plasma testosterone and androstenedione secretion, and at surgery multiple dermoid cysts of both ovaries were found in association with polycystic ovaries. The suggestion that the dermoid cysts may be causative in the evolution of the polycystic ovarian disease has been made. The mechanism of the insulin resistance appears to be at the post receptor level. The acanthosis nigricans diminished following surgery with normalization of the plasma androgens.

Acanthosis Nigricans↗
PubMed1976

A testosterone-producing adrenal cortical adenoma in an elderly woman.

A 76-year-old woman with virilization had menopausal levels of circulating LH and FSH, and a markedly elevated concentration of plasma testosterone (9130 pg/ml) into the range for adult men. Plasma cortisol and androstenedione levels andurinary 17-ketosteroid secretion were normal. Ethinyl estradiol suppressed plasma testosterone, LH, and FSH levels into the normal range for premenopausal women, but the testosterone concentration was unaffected by the administration of dexamethasone or ACTH. Retrograde venous sampling and angiography localized a right adrenal adenoma preoperatively. Following adrenalectomy, there was a prompt fall in testosterone, but there was no change in the LH concentration. Thus, this patient had an adrenal adenoma which secreted only testosterone and appeared to be gonadotropin-responsive. Testosterone levels in the adult male range failed to suppress gonadotropins. The significance of these findings is discussed.

Adenoma↗
PubMed2001

Abnormalities of gonadotrophs in the adenohypophysis of infertile male PD rats.

Male PD strain rats are sterile in the homozygous condition (pd/pd) due to abnormal spermatogenesis detectable at around nine weeks of age. Previous studies have indicated electron microscopic abnormalities in the Sertoli cells of pd/pd males at three and 12 weeks of age. Since spermatogenesis and Sertoli cell function depend on gonadotropins (luteinizing and follicle-stimulating hormones [LH and FSH]) and testosterone, production and/or secretion of these hormones might be altered in pd/pd males. The aim of the study reported here was to investigate the hormonal status of pd/pd males at three, six, and nine weeks of age. Although alteration was not evident in the LH-immunoreactive cells, FSH-immunoreactive cells in pd/pd males were small in size with scant cytoplasm and were reduced in number and area (73 and 51% of phenotypically normal pd/+ males, respectively) at three weeks of age, although serum FSH concentration was similar to that in pd/+ males. At six and nine weeks of age, percentages of the areas occupied by LH- and FSH-immunoreactive cells in pd/pd males were higher than those in pd/+ males. Serum FSH concentration in pd/pd males was significantly high at nine weeks of age, although a difference in serum LH and testosterone concentration was not evident. These results suggest that FSH production in pd/pd males is decreased at three weeks of age. This might be associated with the Sertoli cell abnormalities and subsequent abnormal spermatogenesis seen in adult life.

Animals↗