Testosterone: a major determinant of extragenital sexual dimorphism

Relation between plasma high-density lipoprotein cholesterol and sex hormone concentrations in men

High-density lipoprotein (HDL) cholesterol is inversely associated with risk of heart attack. Sex hormones have been suggested as possible factors contributing to the gender difference of coronary heart disease risk. Little is known about how endogenous sex hormone concentration might be related to HDL cholesterol. The relation was examined in 225 men participating in the Multiple Risk Factor Intervention Trial. Plasma testosterone concentration was positively correlated with HDL cholesterol and the change in testosterone concentration was also positively correlated with change in HDL cholesterol. The relation between testosterone and HDL cholesterol could not be fully explained by age, relative weight, alcohol consumption and cigarette smoking in the cross-sectional study. However, when this relation was examined longitudinally, the partial correlation between changes in testosterone and HDL cholesterol did not quite achieve statistical significance (0.05 less than p less than 0.10). The biologic process that relates HDL cholesterol to testosterone is not known. The results suggest an inverse relation between plasma estradiol concentration and low-density lipoprotein cholesterol, but no statistical significant correlation with HDL cholesterol. In addition, there was no association noted in the current research between estradiol concentrations and the known determinants of HDL cholesterol.

Neonatal sex-steroid hormones and muscular strength of boys and girls in the first three years

Five sex-steroid hormones were assayed in umbilical cord blood. Strength was assessed in children in three samples at several ages from birth to 33 months. At different ages, different strength measures were taken, viz., at birth, prone head responses; at 3 months, leg strength; from 6 to 33 months, grip strength. Boys had higher average strength scores than girls but the sex differences were small and did not increase or decrease over the age period studied. Across-age strength scores showed a significant relation to androstenedione and a significant interaction of sex and progesterone. Both boys and girls with higher strength scores had lower androstenedione. Girls with high cord blood progesterone showed low strength while boys with high progesterone showed high strength. There were no sex differences in androstenedione or progesterone level. The androstenedione finding did not replicate across samples but the Progesterone X Sex interaction was replicated in all three samples. No relationship was found between strength and other hormones assayed: testosterone, estradiol, and estrone.

The effects of gonadectomy on left ventricular function and cardiac contractile proteins in male and female rats

To examine the influence of the sex hormones on mechanical properties and biochemistry of the adult heart, we studied left ventricular function and cardiac contractile proteins in hearts from 20-week-old male and female rats that had been gonadectomized at 18 days of age, compared with hearts from sham-operated animals. Testosterone and estradiol were not detectable in serum from male and female gonadectomized rats, respectively. The male rats had lower body and heart weights than male sham operated rats, whereas these values were higher in female gonadectomized than in female sham-operated rats. Left ventricular function was studied in a working heart apparatus at similar heart rate and at controlled levels of aortic diastolic pressure and left atrial pressure. At moderate left atrial pressure, end-diastolic pressure and volume per gram dry left ventricle were the same in all groups, but at high left atrial pressure, end-diastolic pressure, and volume per gram dry left ventricle were lower in male and female gonadectomized than in the respective sham-operated rats. Further increases in left atrial pressure were associated with mechanical alternans in male and female gonadectomized rats. Significantly (P less than 0.05) lower values for cardiac output, peak systolic pressure, ejection fraction, and myocardial oxygen consumption occurred in male gonadectomized compared with sham-operated rats at moderate and high left atrial pressure at higher levels of aortic diastolic pressure. Decreases in these values for female gonadectomized compared with sham-operated rats occurred only at high left atrial pressure. A significant downward shift in the mean force-velocity relationship was observed in all gonadectomized rats at both moderate and high left atrial pressure. In a follow-up study, when end-diastolic pressure was kept the same at both moderate and high left atrial pressure in female sham-operated and gonadectomized rats by reducing heart rate, decreases in contractile function in gonadectomized rats were observed at all preloads. Ca++-myosin ATPase activity was significantly reduced by 34% in male and by 19% in female gonadectomized rats when compared to respective sham-operated control hearts. These alterations in myosin ATPase activity were associated with a reduction in the V1 myosin isoenzyme and an increase in the V3 isoenzyme. Thus, left ventricular filling and left ventricular function were impaired in hearts of gonadectomized rats. Alterations in function were associated with depressed cardiac myosin ATPase activity in male and female gonadectomized rats.(ABSTRACT TRUNCATED AT 400 WORDS)

Nuclear translocation of estradiol receptors by the in vivo administration of norethisterone: an alternate mechanism for gonadotropin inhibition

In order to investigate the anti-gonadotropic effect of norethisterone (NET) in long-term ovariectomized rats, we studied the interaction of this synthetic progestin with intracellular steroid receptors in the anterior pituitary by a nuclear exchange assay. The results demonstrated that the administration of NET to long-term ovariectomized rats resulted in nuclear translocation of estradiol cytosol receptors in the pituitary and uterus with a rate of accumulation and nuclear retention being similar in both tissues. Accumulation of nuclear estradiol receptors in the pituitary was in agreement with the rate of LH inhibition in NET-treated rats. The results presented in this communication may explain the anti-gonadotropic activity of NET in long-term ovariectomized rats in addition to its well known progestational activity.

Physiology of sexual behavior. Embryologic organization and adult activation

Recent studies suggest that sexual behavioral function should be integrated into the framework of sexual physiology as a neuroendocrine phenomenon. Evidence of embryonic neuronal induction and subsequent adult activation and functioning of sex specific circuitry is reviewed.

Toxicity of mercuric chloride to the developing rat kidney. I. Postnatal ontogeny of renal sensitivity

Although the sensitivity of the adult rat kidney to mercuric chloride has been widely reported, the degree to which this toxicant affects the developing kidney is unknown. Therefore, this study examined the effects of HgCl2 on renal function during postnatal maturation. Sprague-Dawley rats were treated with a single sc injection of 5 mg/kg HgCl2 on Day 1, 8, 15, 22, or 29 after birth. The effects on renal function, histology, and morphology were assessed 24, 48, and 120 hr after each treatment. Measurements of renal function included urine volume, osmolality, the ability to concentrate urine during water deprivation, urinary pH, chloride and protein content, tests for glucosuria, hematuria, and various serum chemistry parameters. Rats were killed and their kidneys processed and examined by light microscopy. The renal sensitivity to HgCl2 increased throughout maturation for every parameter measured. No pups treated with HgCl2 on Day 1 died, but mortality increased to almost 20% in rats treated 22 and 29 days after birth. Body weight was unaffected in Day 1 animals, but was decreased at 120 hr post-treatment in three of the other four age groups. Kidney weights were unaffected in 1- and 8-day olds, but were increased by 10 to 55% in rats that were 15, 22, and 29 days old. Urine volume was increased 48 to 72 hr following treatment at all ages. The ability to concentrate urine in response to water deprivation was compromised in all animals with the exception of those treated on Day 1, and was decreased to the greatest extent in 29-day-olds. Urinary chloride concentration was decreased in Day-22 animals at 24 and 48 hr, and in Day-29 rats at all times observed after injection. Urinary pH was more acidic in treated suckling pups, and more basic in treated pups after weaning on Day 22. Urinary protein content was increased after exposure in all but the pups treated on Day 1. Serum creatinine was increased at 120 hr after injection in Day-8 rats, and 24 and 48 hr after injection in older rats. Glucosuria and hematuria occurred with increasing frequency as the pups matured. Histological evaluation revealed some cortical tubular dilatation in rats treated on Day 1 or Day 8; there was tubular necrosis in older rats. For all parameters observed, the neonatal kidney was largely insensitive to HgCl2 toxicity; however, a trend toward increased sensitivity with increasing age was demonstrated.

Analysis of thymocyte subpopulations following treatment with sex hormones

Sex steroids were found to affect both murine and avian immune systems. Female and male (NZB X NZW)F1 mice were castrated at 2 weeks of age and given Silastic implants containing either dihydrotestosterone or estradiol. Four weeks following treatment, the thymuses were studied for cell cycle kinetics and for the presence of various cell surface antigens using fluorescein-conjugated antisera and flow cytometric techniques. Estradiol therapy resulted in an increase in mature thymocytes, that is, thymocytes that had decreased peanut agglutinin receptors and decreased Thy 1 antigens on their surfaces. Additional studies with anti-Lyt 1 and 2 indicated that these mature thymocytes were of the "helper" rather than the "suppressor" phenotype. Estradiol therapy resulted in an increase in the percentages of proliferating cells in the spleen and a decrease in the percentages of proliferating cells in the thymus. In contrast, in the avian system, estradiol had little effect on proliferation in immunological organs. Dihydrotestosterone was a potent inhibitor of proliferation in the avian bursa. These results indicate that sex hormones have specific effects on different immune cell subpopulations. In the murine system the male is the heterogametic sex but in the avian system the female is the heterogametic sex. Based upon the present and previous studies, we suggest that the primary modulating hormone for immunological sex effects in the mammal is estrogen, whereas in the bird it is androgen.

Residual androgen binding in testicular feminization (TFM)

Most mutants with genetic androgen-resistance possess some level of androgen binding which exhibits properties of receptors. The present studies aim to determine whether the androgen binding activities in mutants are, or are related to, receptors. This binding portion is termed residual androgen receptors. We have examined several androgen-resistance mutants with testicular feminization (TFM). Putative androgen receptors from mice, rats, and humans with TFM have been compared, and at least three different types of residual receptors have been observed. They are discussed in relation to possible receptor defects and to differences in the nature of androgen-resistance associated with each of them.

High fetal estrogen concentrations: correlation with increased adult sexual activity and decreased aggression in male mice

In the house mouse (Mus musculus), fetuses may develop in utero next to siblings of the same or opposite sex. The amniotic fluid of the female fetuses contains higher concentrations of estradiol than that of male fetuses. Male fetuses that developed in utero between female fetuses had higher concentrations of estradiol in their amniotic fluid than males that were located between other male fetuses during intrauterine development. They were also more sexually active as adults, less aggressive, and had smaller seminal vesicles than males that had developed between other male fetuses in utero. These findings raise the possibility that during fetal life circulating estrogens may interact with circulating androgens both in regulating the development of sex differences between males and females and in producing variation in phenotype among males and among females.

Hormonal control of sexual differentiation: changes in electric organ discharge waveform

Males and females of some mormyrid electric fishes generate electrical pulses that differ in waveform and duration. For one such species, testosterone or dihydrotestosterone induces females and immature males to produce the mature male electric organ discharge which is two times the duration of the female or immature discharge. Estradiol has only a weak effect. For a second species where males and females have similar electric organ discharges, testosterone produces no effect. The data suggest that androgens affect the electric organ itself.

Inhibition of polyamine synthesis blocks urinary secretion of beta-glucuronidase from mouse kidney

The effect of inhibition of polyamine synthesis on castrated male mouse kidney beta-glucuronidase induction and secretion by testosterone was studied. Inhibition of the activities of polyamine synthesis key-enzymes, L-ornithine and S-adenosyl-L-methionine decarboxylases, was performed with the combined treatment of 2-difluoromethylornithine and methylglyoxal' bis(guanylhydrazone). Blockage of polyamine synthesis did not affect testosterone-induced increase in renal beta-glucuronidase but blocked its secretion into the urine. After withdrawal of inhibitor-treatment beta-glucuronidase secretion normalized, and repeated testosterone administration produced undisturbed beta-glucuronidase secretion peak in urine suggesting that blockage of beta-glucuronidase secretion was not due to the tissue damage produced by inhibitors. These results indicate that the stimulation of renal polyamine synthesis by testosterone is not necessary for the induction of beta-glucuronidase but is required for the urinary secretion of this protein.

Sex differences in the pattern of steroid accumulation by motoneurons of the rat lumbar spinal cord

We previously reported that male rat lumbar motoneurons accumulate radioactivity after injection of tritiated testosterone (T) or dihydrotestosterone (DHT), but not estradiol (E). We now report autoradiographic evidence that lumbar motoneurons in male rats accumulate T or its metabolites more frequently than do female motoneurons. However, this sex difference in hormone accumulation by motoneurons is not observed following the injection of DHT or E, both of which are normal metabolites of T. Very few motoneurons from any population accumulated E or its metabolites. In fact, some motoneurons had fewer silver grains over their nuclei than would be expected by chance, thus suggesting that these cells not only failed to accumulate E or its metabolites, but actively or passively excluded them from their nuclei. Virtually every motoneuron of either sex accumulated hormone after DHT injection. Following T injection, more motoneurons were labeled in males (72-77%) than in females (28-39%), indicating a sex difference in hormone accumulation. Taken together, these results suggest that either (1) there are separate receptors for T and DHT, and motoneurons have more T receptors (but equal numbers of DHT receptors) in males than in females, or (2) the motoneurons of male rats have greater access to systemically administered T or its metabolites than do those of females.

DNA sequence polymorphism in an androgen-regulated gene is associated with alteration in the encoded RNAs

We have used plasmid pMK908, whose cDNA insert corresponds to an androgen-inducible RNA from mouse kidney, as a probe to study both the complementary genomic DNA and the encoded RNA sequences in several inbred strains of mice. A polymorphism in the 908 structural gene, revealed by Southern blotting of HindIII-generated DNA fragments, was found to map near the Gpi-1 and Tam-1 loci on chromosome 7. The 908 structural gene has been termed RP2. The 908 RNAs constitute a sequence-related group displaying extensive size heterogeneity. This heterogeneity, reflected in the size distribution of the RNA on electrophoretic blots, is controlled by a genetic site that is tightly linked to RP2. Thus, associated with polymorphism at RP2 is a change in the molecular size pattern of encoded transcripts.

Progestins can mimic, inhibit and potentiate the actions of androgens

There is an extensive background on the androgen responsiveness of the mouse kidney which can be demonstrated histologically by hypertrophy of the Bowman's capsule and the proximal convoluted tubule. Although androgens increase many renal proteins, beta-glucuronidase and ODC are distinguished by exquisite genetic regulation of the magnitude of the response induced by testosterone. Both the qualitative and quantitative expression of the genes for these enzymes are strain specific, and are dependent upon regulatory alleles. Ornithine decarboxylase is of particular interest since the response of this enzyme is rapid compared to that of beta-glucuronidase. Recent studies using a newly developed androgen receptor assay have demonstrated that the duration of retention of the androgen receptor complex in the nucleus correlates with the magnitude of the androgenic response. Progestins can mimic, inhibit, or potentiate the action of androgens. These responses have been termed the androgenic, antiandrogenic and synandrogenic actions of progestins, respectively. The androgenic and antiandrogenic action of this class of steroids are manifest on many tissues and on many endpoints within a given organ. These effects are believed to involve an early step(s) of androgen action which is common to all sensitive tissues. Results to date suggests that this early step involves the androgen receptor. By contrast, the synandrogenic action of progestins is limited in that it is not observed on all tissues, and not even on all endpoints within a single organ. In the mouse kidney, the synandrogenic actions of progestins have been most extensively studied on beta-glucuronidase. With this enzyme this unusual response to progestins can be demonstrated only in mice which carry the Gus-ra allele. This observation suggests that the potentiating action of progestins on beta-glucuronidase is manifest directly on the Gus gene complex. It is not certain at this time whether a similar mechanism is involved in the potentiation of androgen action on other organs such as the prostate. The androgenic action of progestins is believed to be similar to that of other androgens. Androgenic progestins such as MPA bind to the androgen receptors and translocate them to nuclei. This is followed by a dose dependent increase of proteins similar to what is observed after testosterone administration. In addition, the regulatory genes which modulate androgen action have the same effect on the androgenic effect of progestins. The fact that the potency of progestins such as MPA is less than that of testosterone is believed to relate in part to their lower affinity for the androgen receptors.(ABSTRACT TRUNCATED AT 400 WORDS)

Relative binding affinities of testosterone, 19-nortestosterone and their 5 alpha-reduced derivatives to the androgen receptor and to other androgen-binding proteins: a suggested role of 5 alpha-reductive steroid metabolism in the dissociation of "myotropic" and "androgenic" activities of 19-nortestosterone

The relative binding affinities of testosterone (T), 19-nortestosterone (N) and their 5 alpha-reduced derivatives: 5 alpha-dihydrotestosterone (DHT) and 5 alpha-dihydro-19-nortestosterone (DHN) to the androgen receptor of the rat seminal vesicle was studied using competition experiments. In cell-free extracts incubated at +10 degrees C for 18 h the relative binding affinities of these steroids (DHT greater than T = DHN = N) proved to be specific for the androgen receptor, in the sense that only prostatic extracts gave a similar result while three other androgen binding proteins (human sex steroid binding globulin, rat epididymal androgen binding protein and an antibody raised against T) exhibited quite different binding specificities. In minced seminal vesicles incubated at 37 degrees C for 1 h the binding affinities showed marked differences (DHT greater than N greater than T greater than or equal to DHN) and similar patterns were observed with both the cytoplasmic and the nu clear receptors. Our findings suggest that (I) the simultaneous presence of a 4-ene double bond and 19-methyl group in T does not favor the tight binding of T to the androgen receptor; therefore, either saturation of this double bond or elimination of the 19-methyl group leads to increased binding and (II) while 5 alpha-reduction of T increases the affinity of this steroid to the receptor, that of N does not influence or rather tends to decrease the binding affinity. The opposite changes observed in the binding affinities of T and N after their 5 alpha-reduction may account for the lower androgenicity of N. On the other hand, the relative myotropic activity in vivo of these steroids is apparently determined by the ratio of their affinities (N/T approximately 3 at 37 degrees C) to the androgen receptor.

Hormonal replacement and sexuality in men

Only in the last few years has the scientific study of hormonal replacement therapy for hyposexuality begun in earnest with the advent of appropriately controlled experiment studies. Dose-response relationships can be demonstrated between testosterone (T) and sexual measures, but these have not yet been investigated in detail. Some aspects of sexual function are maintained in the presence of androgen levels well below the normal range, but preliminary evidence suggests that within a normal population high levels of T are correlated with more vigorous responses to visual erotic stimuli. Though T (and to a greater extent free T) declines with aging in parallel with the decline of sexual function, these hormonal changes contribute only to a minor extent to the behavioural change. Some non-aromatizable androgens may be less effective in stimulating sexual behaviour than T, but initial data on effects of dihydrotestosterone suggests that the capacity of an androgen to be aromatized (converted to oestrogen) is not a requirement for its sexual action. While T apparently increases the incidence of all types of male sexual activity, recent data contradict the belief that it directly facilitates the erectile mechanism in men, even though erection frequency is greatly reduced in untreated hypogonadal men. At the present juncture, it appears that the initial action of T may be on libido factors which lead in turn to the stimulation of other aspects of sexuality. Specifically, we propose that androgen acts through stimulating genital sensations and/or other pleasurable awareness of sexual response rather than directly through cognitive processes such as sexual imagery.

Hormones and psychosexual differentiation: implications for the management of intersexuality, homosexuality and transsexuality

During fetal development of subprimate mammals, sexual differentiation of the genitals and of specific sex-dimorphic brain systems depends on androgens; corresponding sex differences are displayed in prepubertal behaviours as well as in behaviours that depend on activation by pubertal hormones. In human beings, fetal hormones play the same role in genital differentiation. Hormone-dependent structural brain changes are also very likely but have not yet been demonstrated. The corresponding effects of fetal hormones on childhood behaviour have been found both in subhuman primates and in man, while the evidence concerning later behaviour, including sexual orientation, is not yet clear. The development of gender identity in humans is a cognitive process that has no counterpart in animal behaviour and is unlikely to be based on a specific hormone-sensitive brain system. It appears that the hormone-dependent variations of sex-dimorphic behaviour in childhood can be accommodated within either gender identity, provided that the child's physical appearance is gender adequate and the parental (or other caregivers') rearing style does not interfere with typical gender role development. In intersex individuals, changes in gender identity seem to occur primarily when genital and/or general physical appearance are in conflict with the assigned gender and/or when rearing has been ambiguous. The available descriptions of such changes do not seem compatible with a primarily neuroendocrine explanation. Thus, decisions on sex assignment and reassignment of intersex patients need to be based on expected social and sexual functioning, and the clinical management of such patients must minimize the risk of ambiguous rearing and of the development of a gender-incongruent physical appearance. The development of a sexual orientation in humans as hetero- or homosexual does not seem to depend on pubertal hormones. The evidence for a role of fetal hormones is suggestive, but the issue is not yet settled. Attempts to implicate the H-Y antigen in the aetiology of transsexuality seem to have failed; psychoendocrine research here parallels that on sexual orientation. Some recent developments in the management of transsexual patients are discussed.

3 alpha, 17 beta-androstanediol glucuronide in plasma. A marker of androgen action in idiopathic hirsutism

Biologically active androgens and peripheral androgen metabolites in plasma were measured in 25 women with idiopathic hirsutism (IH). Plasma testosterone was not significantly elevated. Free testosterone however was increased although the elevation was not impressive (10.9 +/- 6.6 SD vs. 3.3 +/- 1.5 ng/dl) and one-fourth of the cases had normal unbound testosterone. Dihydrotestosterone (DHT) values were elevated (23.5 +/- 14 vs. 12.5 +/- 3.59) but again over half of the values were within the normal range. In our series of mild to moderate cases, 3 alpha-diol was not at all discriminatory. However, plasma 3 alpha-diol glucuronide was markedly increased (604 +/- 376 vs. 40 +/- 10 ng/dl), and elevated in all but one mild case. Previous studies document that DHT is the important androgen in skin and formation of DHT and 3 alpha-diol is markedly increased in vitro in IH. Since 3 alpha-diol glucuronide is derived largely from extrasplanchnic events, beta-glucuronidase is present in skin, and androgen stimulates formation of the enzyme in extrasplanchnic tissue, we conclude that 3 alpha-diol glucuronide is a marker of peripheral androgen action and markedly elevated in IH.

Stereotyped behavior elicited by amphetamine in the rat: influences of the testes

Castrating male rats in adulthood increased the duration of stereotyped behavior in responses of 5 mg/kg injections of d-amphetamine sulfate; exogenous treatment with testosterone propionate (TP) reversed this effect. Ovariectomy in adulthood had no effect on stereotypy, but TP injections reduced stereotyped responding by ovariectomized females. Thus testosterone exerts comparable effects on stereotypy elicited by amphetamine in both sexes. Males castrated at 1, 6 or 10 days of age but not males castrated in adulthood displayed levels of stereotyped behavior comparable to those of ovariectomized females when all animals were given TP in adulthood. Control experiments indicated that age of castration rather than time since castration was the critical factor, implying that secretions of the testes early in life exert effects on systems that regulate the responses of adults to amphetamine.

Plasma testosterone, high density lipoprotein cholesterol and other lipoprotein fractions

High density lipoprotein (HDL) cholesterol levels are strongly related to risk of heart attack. Identification of determinants of high density lipoprotein cholesterol may provide important information concerning the cause of heart disease. The relation between one possible determinant, testosterone, and high density lipoprotein cholesterol and other lipoprotein fractions was evaluated in 247 middle-aged men. The results indicate that testosterone levels (both free and total) were positively correlated with high density lipoprotein cholesterol (r = +0.24, p less than 0.01) and negatively correlated with triglycerides and very low density lipoprotein cholesterol. The association between testosterone and high density lipoprotein cholesterol could not be explained by intake of alcohol, obesity, age, smoking or physical activity. Furthermore, the relation of testosterone to HDL cholesterol was independent of the relation of testosterone to very low density lipoprotein (VLDL) cholesterol or triglycerides.

Oestrogen receptor proteins in malignant and fetal pancreas

High levels of high-affinity oestrogen binding were detected in cytosolic and nuclear fractions of tumour tissue from six patients with pancreatic carcinoma. Similar binding was found in fetal but not in normal adult pancreas, making depression of fetal genes a possibility. Specific androgen binding was not detectable. These findings suggest that anti-oestrogen treatment may offer a new approach to the treatment of pancreatic carcinoma.

Sexual differentiation of the central nervous system

Sexual differentiation of reproductive and behavior patterns is largely effected by hormones produced by the gonads. In many higher vertebrates, an integral part of this process is the induction of permanent and essentially irreversible sex differences in central nervous function, in response to gonadal hormones secreted early in development.