Higher Plasma Testosterone Levels Research Articles

Non-gonadal mediated effect of photoperiod on hibernation and body weight cycles of the European hamster

1. 1. Sexually active male European hamsters raised under short photoperiod display high levels of plasma testosterone, high body weight and do not hibernate. 2. 2. Castrated males in May, raised under the same conditions, do not hibernate and do not present the physiological body weight rhythm. 3. 3. Normal and castrated animals under natural conditions enter hibernation and display a normal body weight rhythm. 4. 4. Normal and castrated animals not submitted to the natural succession of long and short days do not enter hibernation. 5. 5. Photoperiod directly controls body weight and hibernation without gonadal interactions.

Androgen levels and erythrocytosis in maturing brown trout,Salmo trutta L.

The number of circulating erythrocytes was monitored in two strains of brown trout during the spawning season. Erythrocyte numbers were significantly elevated in mature male fish of both strains compared with mature females or immature fish. This period of erythrocytosis coincided with elevated plasma 11-ketotestosterone levels in mature male fish, was out of phase with the testosterone peak in males and was not observed in females despite high levels of plasma testosterone. The results are discussed with reference to the control of erythropoiesis in higher vertebrates.

Demonstration of an odorous intramale primer effect in short-tailed vole,Microtus agrestis L.

Anal (proctodeal) glands of maleMicrotus agrestis housed in social isolation undergo severe atrophy. Their weight and volume is significantly lower than those of the stock control males. The atrophied glands can be revived by subjecting deprived voles to various social odors. Atrophied glands of isolated males do not respond to the odors of male and female urine, voided feces of females, and unvoided feces of males. Atrophied anal glands of males exposed to voided male feces (which have passed the orifice of the anal gland) and soiled bedding from adult males show strong recrudescence. The mean weight and volume of the glands and plasma testosterone level are significantly higher than of males maintained in complete social isolation, although they are significantly less than those of stock control males. Atrophied glands of socially deprived males strongly respond to the odor of ethereal extract of gland secretion. In males exposed daily to anal gland secretion extract, the weight and volume of the gland and plasma testosterone level increase and are not significantly different from those of stock controls. They enjoy higher plasma testosterone levels and consequently larger and more active anal glands than complete isolates.

Dose and time effects of treatment with low doses of a LRH agonist on testicular axis and accessory sex organs in rats.

LRH and its agonists have been shown to exert both stimulatory and inhibitory effects on testicular function. In the present study, the dose and length of treatment were tested to determine the appearance of the stimulatory and inhibitory effects of LRH agonist on testicular axis including the three levels. Two doses of an agonist of LRH, 40 and 100 ng/100 g body weight (buserelin, 'agonist'), were administered daily for 1 to 15 days to adult male rats. Control rats received the vehicle only. On day 1, 2, 4, 8 and 15 of treatment, the pituitary, testicular and peripheral levels (weight of accessory sex organs and androgen receptors in ventral prostate) were tested 6 h after the last injection. For the 15 days of treatment with both doses, a stimulatory effect of the 'agonist' was observed on LH and FSH release. A short exposure (1-2 days) to the low dose of the 'agonist' had a stimulatory effect on the density of LH/hCG testicular receptors (326 +/- 49 vs control 185 +/- 21 fmol/mg protein, mean +/- SEM), on the weights of seminal vesicles and ventral prostate and exposure to both doses led to high plasma testosterone levels (13.8 +/- 0.5 and 13.7 +/- 0.7 ng/ml, respectively, vs control 2.6 +/- 0.3 ng/ml), and to an increased density of nuclear androgen receptors in the ventral prostate (142 +/- 9 and 144 +/- 15 fmol/mg protein respectively vs control 97 +/- 12 fmol/mg protein).(ABSTRACT TRUNCATED AT 250 WORDS)

Possible role of prolactin in the inhibitory effect of testosterone on the hypothalamic-pituitary-testicular axis in the rat.

To study the role of testosterone on the regulation of the hypothalamic-pituitary-testicular axis, young intact male Wistar rats were given acute (24 h) or chronic (5 days) subcutaneous treatments of 500 micrograms testosterone propionate (TP) or vehicle alone. Plasma LH, prolactin and testosterone levels were measured both basally and after administration of LH-releasing hormone (LHRH) or human chorionic gonadotrophin (hCG) by means of specific radioimmunoassay systems using materials supplied by the NIADDK. After acute treatment with TP there was an increase in basal plasma testosterone concentrations and no modification in the hCG response when compared with vehicle-treated animals. No difference could be detected in basal plasma testosterone levels after the chronic treatment, but a significant reduction in the hCG response was observed. Both acute and chronic treatments with TP resulted in a significant decrease of basal plasma LH levels. A reduced LH response to LHRH in acutely treated rats and no response in the chronically treated rats was detected. Plasma prolactin levels showed an increase after both acute and chronic treatments. To evaluate the possible role of the increased plasma prolactin levels on the above modifications during TP treatment, another group of animals was treated with TP and bromocriptine (dopamine agonist) simultaneously to avoid the increase in plasma prolactin levels. In this situation, neither basal plasma LH levels nor the response to LHRH were altered when compared to vehicle-treated rats; a normal testosterone response to hCG stimulation was observed in spite of the high basal plasma testosterone levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Differential symptom response to parenteral estrogen and/or androgen administration in the surgical menopause

The investigation of estrogen and/or androgen administration on physical and psychological symptoms in the surgical menopause was carried out in a prospective, double-blind, crossover design. When patients who received either a combined estrogen-androgen drug or androgen alone were compared with those who received estrogen alone or placebo, energy level, well-being, and appetite were increased (p < 0.01). The androgen-containing preparations also induced lower somatic, psychological, and total scores on the menopausal index. Superior functioning in the androgen-treated groups occurred in association with higher plasma testosterone levels during the treatment phases (p < 0.01). These data suggest that reduced levels of circulating testosterone subsequent to bilateral oophorectomy may play an important role in the development of physical and psychological symptoms that are frequent sequelae of this surgical procedure.

Passage of testosterone, testosterone propionate and testosterone enanthate from silastic implants and the retention of testosterone once it enters the blood of ewes

Two studies were conducted to determine the passage of testosterone, testosterone propionate and testosterone enanthate through silastic implants and to determine the retention of the three hormones once they enter the blood. In the first experimental, ovariectomized ewes with implants containing testosterone propionate and ewes with implants containing testosterone enanthate had higher levels of plasma testosterone than ewes with implants containing testosterone. Testosterone enanthate implants released more hormone during the 13-day period than the testosterone propionate and testosterone implants and testosterone propionate implants released more hormone than testosterone implants. In the second experiment, concentrations of plasma testosterone were elevated longer for ovariectomized ewes intravenously administered testosterone propionate, than ewes receiving testosterone or testosterone enanthate intravenously.

Endocrine control of antler growth in red deer stags.

Observations of body weight, testis size, antler status, plasma testosterone and prolactin were made on 12 red deer stags during their first 2 years of life. Six of the stags were fed to appetite throughout the study (Group A) and 6 were fed a 70% restricted diet during each winter (Group B). In addition 6 of the stags , 3 from each group, were studied in more detail; LH and testosterone were measured either after a single injection of LH-RH or in samples taken at frequent intervals over a period of 8 or 24 h. During the study the stags became sexually mature, developed first their pedicles and then antlers and showed at least one complete cycle of casting and regrowth of the antlers . The stags in Group A developed their testes and pedicles about 2 months earlier than did those in Group B. Pedicle initiation was associated with increasing plasma testosterone levels in response to changes in LH secretion, and antler development occurred when testosterone levels were low or decreasing. Cleaning of the velvet was associated with high levels of plasma testosterone. Antler casting occurred when plasma testosterone concentrations were low or undetectable and prolactin levels were high or increasing. The relationship between LH and testosterone varied during the study; in spring when the testes and antlers were growing, relatively high levels of LH were associated with only small peaks of testosterone, yet in summer, when antler growth was complete and the antlers were clean of velvet, low LH concentrations were associated with large peaks of testosterone.

The Immediate Effect of HCG Upon Plasma Testosterone Levels in the Bull

No effect of HCG upon the plasma testosterone level in 16 bulls was seen the first 5 or 15 min after injection. In 8 bulls receiving 750 or 1500 i.u. HCG by intravenous injection a lag time of 30 min occurred before plasma testosterone response could be measured. The high plateau level of plasma testosterone concentration was reached approximately 1 h after injection. Following intramuscular injection of 750 i.u. or 1500 i.u. HCG a lag time of 45–60 min was observed for the testicular response measured as elevated plasma testosterone level. The high plateau levels of plasma testosterone in these bulls were reached approximately 1½ h post injection.

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Testicular tumors in King-Holtzman hybrid rats with testicular feminization (tfm) were seen as firm, rounded masses of tissue consisting of Leydig cells, myoid cells, and fibroblast-like cells. The cytoplasm of Leydig cells contained well-developed smooth endoplasmic reticulum, pleomorphic mitochondria with numerous cristae, and many lipid droplets. Mitochondria were numerous and varied in size and shape. Their cristae were in the form of tubules, and lipid-like inclusions were frequently seen in the mitochondrial matrix. Lysosomes, rough endoplasmic reticulum, and Golgi bodies were also scattered in the cytoplasm. An in vitro study showed that more testosterone was produced in the tumor than in the testes of rats with tfm; however, the amount in both was less than normal. Testicular tumor-bearing rats with tfm exhibited slightly higher levels of plasma testosterone than did non-tumor-bearing animals with tfm. Levels in both were significantly higher than normal. Testicular tumor cells growing in culture medium supplemented with luteinizing hormone (LH) contained more protein and synthesized more androgen and DNA than did those growing in culture medium without LH. Observed under the scanning and transmission electron microscopes, the LH-stimulated cells had well-developed cytoplasmic organelles and inclusions and surface specializations such as numerous microvilli, large blebs, and other microextensions. They adhered well to the glass surface. These results indicated that Leydig cells in testicular tumors of rats with tfm had morphologic characteristics of steroid-producing cells. In addition these cells were capable of producing steroids, and this capability was enhanced by the presence of LH.

Malignant Transformation of Polyostotic Fibrous Dysplasia

We have described an unusual case of polyostotic fibrous dysplasia in a 25-year-old white woman who had malignant transformation into a mesenchymal tumor with widespread metastases and features of rhabdomyosarcoma. Masculinization also occurred with high plasma testosterone levels. A mechanism for the development of masculinizing features is discussed.

Testosterone levels in female partners of infertile couples: Relationship between androgen levels in the woman, the male factor, and the incidence of pregnancy

Plasma testosterone levels were measured in the female partners of 146 consecutive infertile couples. The incidence of hyperandrogenism in the woman was correlated with ovarian function, incidence of pregnancy, male factor, and response of plasma testosterone levels to prednisone treatment. Over 70 per cent of the patients had pretreatment testosterone levels above 40 ng. per 100 ml. while after a minimum of two months of therapy approximately 80 per cent had levels below 40 ng. per 100 ml. High levels of plasma testosterone were associated with significant prolongation of the follicular phase of the cycle and increased incidence of amenorrhea or anovulation. An over-all pregnancy rate of 50.4 per cent resulted from the treatment. A direct relationship between pregnancy rates and sperm density as well as between pregnancy rates and degree of suppression of plasma testosterone after therapy was observed. These results demonstrate a high incidence of hyperandrogenism in female partners of infertile couples. The effectiveness of glucocorticoid treatment appears to be related to suppression of excessive androgen levels. The data also suggest that infertility is a relative state related to the fertility potential of each member of the couple. Improvement of the fertility potential of either member may result in conception.

HYPOTHALAMO‐PITUITARY‐GONADAL FUNCTION IN MALE CENTRAL PRECOCIOUS PUBERTY

Eleven boys aged 1-10 years with central precocious puberty were studied. According to the pubertal development six were classified as P2, one as P3 and four as P5. In all cases plasma testosterone levels were definitely elevated (1.7-5.8 ng/ml) when compared with pre-pubertal controls. Peak values after HCG (3 X 1500 units) in four of the boys were in the high adult range. The binding capacity of serum testosterone oestradiol binding globuline (TeBG) ranged between 0.5 and 7.30 microgram/dl. Basal plasma levels of LH and FSH were respectively 2.06 +/- 0.64 and 1.2 +/- 0.25 miu/ml, and peak levels after LHRH (0.1 mg/m2) 13.9 +/- 3.7 and 2.6 +/- 0.43 miu/ml respectively. The data demonstrated a significant increase of plasma testosterone and post LHRH LH peak levels in boys with central precocious puberty when compared with pre-pubertal controls. The patients at stage P2 exhibited high levels of plasma testosterone contrasting with the degree of pubertal maturation, high values of TeBG and low response to LHRH which were in the pre-pubertal range. These findings suggest that the testicular sensitivity to LH increases early in boys with central precocious puberty, while the testosterone responsiveness, both at peripheral and hypothalamic levels, is delayed.

Effects of ewe proximity on peripheral plasma testosterone levels and behaviour in the ram.

Groups of yearling and immature rams were kept for 6 months during the breeding season either adjacent to or apart from ovariectomized ewes in which oestrus was induced by hormone therapy. The older rams kept near ewes were found to have larger testes, higher plasma testosterone levels and greater sexual and aggressive activity, although the immature animals showed no response. Plasma testosterone concentration was also found to increase after copulation in some animals.

Intracranial cycloheximide: Effect on male mouse sexual behavior and plasma testosterone

Cycloheximide (Cyclo), an inhibitor of protein synthesis, infused bilaterally into the preoptic area (POA) of intact B6D2F 1 male mice significantly inhibited male sexual behavior when the males were presented with receptive females 12 hr after treatment. The few males that ejaculated appeared to copulate normally. This finding suggests that Cyclo acts primarily by inhibiting sexual arousal rather than sexual performance. The inhibition of sexual behavior was not observed when the males were tested 84 hr after treatment. After exposure to an estrous female, plasma testosterone levels were measured in males with POA infusions of Cyclo or saline vehicle. No significant difference was found, but both groups had significantly higher levels of plasma testosterone than males not exposed to estrous females. It is suggested that the interference with sexual behavior by Cyclo was not due to interference with the neuroendocrine mechanisms controlling blood andorgen levels, but due to Cyclo acting directly on the neural circuits controlling sexual responsiveness.

Strange females increase plasma testosterone levels in male mice.

Male house mice paired with a normal female for 1 week do not have higher plasma testosterone levels than do males that remain in all-male groups, but paired males have markedly elevated testosterone levels 30 to 60 minutes after the resident female is replaced by another female. Elevation of testosterone levels in these males is similar to that in isolated males paired with a female, does not depend on copulation with the strange female, occurs under housing conditions that permit continuous exposure to the odors of other females and males, and does not occur when the resident female is replaced by another male for 30 to 60 minutes. The elevation thus appears to be a specific endocrine response to an encounter with a strange female. These results, along with previous findings suggesting that strange males affect endocrine function in females, indicate that bisexual encounters are likely to produce endocrine changes in members of both sexes.

THE EXCRETION OF INDIVIDUAL ADRENOCORTICAL STEROIDS DURING NORMAL CHILDHOOD AND ADOLESCENCE

The excretion of 7 individual 17-oxosteroids and 7 individual corticosteroids in 24 h urine samples from 62 normal infants, children and adolescents, based on an accurate and specific paper chromatographic method for their separation and quantitation, is reported. The excretion of the 11-deoxy-17-oxosteroids gradually increases from 7 years of age and the increase becomes more rapid 2 or 3 years before the clinical signs of puberty appear. The rise continues throughout puberty and beyond it until the adult level is reached. The increase far exceeds that which would be accounted for by the growth of the individual. The increase in the excretion of the 11-oxy-17-oxosteroids with age is much more gradual. Androgens favour the formation of 5alpha metabolites and the 5alpha:5beta ratio of the total 5alpha 17-oxosteroids and the total 5beta 17-oxosteroids shows a statistically significant increase with age. In addition, a relatively high 5alpha:5beta ratio is noted in male infants, which is likely to be related to their relatively high plasma testosterone levels. The excretion of the 17-hydroxycorticosteroids and the alpha-ketolic metabolites of cortisol gradually rises with age and correlates with body weight. The alpha-ketolic metabolites of corticosterone are relatively high in infancy, but after the age of 4 years their excretion also correlates with body weight. An increase in the 5alpha:5beta ratio of allo-THF to THF is noted at puberty similar to that found with the 5alpha:5beta ratios of the 17-oxosteroids.

Changes in testicular leydig cells and in plasma testosterone levels among seasonally breeding rock hyrax.

Seasonal changes in plasma testosterone levels and in various testicular parameters were studied in 41 adult male rock hyrax (Procavia habessinica). Among animals collected during the annual breeding season, testis weights and plasma testosterone levels were approximately five times greater than among animals collected outside the breeding season. Light microscopic measurements showed that increase in testis weight was largely due to enlargement of the seminiferous tubules. Histological sampling techniques indicated no significant change in Leydig cell numbers. Leydig cell size increased during the breeding season, and average Leydig cell volume showed significantly positive correlation with plasma testosterone level. With the electron microscope, Leydig cell hypertrophy was seen to involve changes in quantity and structure of several cytoplasmic constituents. Lipid droplets disappeared and smooth endoplasmic reticulum (SER) spread dramatically as the cells increased in size. In contrast to the sparse and heterogeneous assemblage of irregularly tubular and cisternal SER seen in nonbreeding animals, the extensive masses of SER in breeding animals appeared as relatively straight, unbranched tubules of uniform diameter. Peculiar membranous structures, possibly derived from the SER, were abundant in the periphery of Leydig cells from animals with high plasma testosterone levels. These findings suggest that there is a definite relationship between plasma testosterone levels and Leydig cell fine structure in seasonally breeding hyrax.

Testosterone production and metabolic clearance rates in sexually mature male and female skate (Raja radiata).

Testosterone production and metabolic clearance rates (MCR) were measured in skate to evaluate their role in maintaining the high testosterone levels found in the plasma of this fish. The results indicate that testosterone production rates in the skate are very low and that the high levels of plasma testosterone are primarily the result of a low metabolic clearance rate. Metabolic clearance rates were determined by the method of continuous infusion. The mean plasma MCR obtained for females (10.4 ±0.42 ml/kg/hr) was significantly higher thanthat of the males (7.93 ±0.57 ml/kg/hr). Plasma testosterone was determined using gas-liquid chromatography after prior purification by thinlayer and paper chromatography. Testosterone levels in plasma samples taken at 9:30 AM were significantly higher than in 5 :30 PM samples. At 9:30 AM, the mean plasma testosterone concentration in the males (5.8 ±1.1 μg/100 ml) did not differ significantly from that of the females (3.8 ±0.73 μg/100 ml). However, at 5:30 PM the values obtained for the sexes were significantly different (males 3.6 ±0.45 μg/100 ml, females 1.8 ±0.39 μg/100 ml). Testosterone production rates were determined as the product of the MCR and the plasma concentration of the steroid. No significant differences were observed between the production rates of the 2 sexes. The average testosterone production rates obtained were 0.38 ±0.07 μg/Kg/hr for the males and 0.33 ±0.05 μg/kg/hr for the females. (Endocrinology85: 552, 1969)