Endogenous Plasma Testosterone Research Articles

P.3.010 Endogenous plasma testosterone in healthy men is negatively associated with hippocampal serotonin receptor 4 binding

Dopamine D2/D3 receptor availability at rest and its association with individual pain perception was investigated using the [11C] raclopride PET-method in 24 female Fibromyalgia (FMS) participants with (FMS+, N=11) and without (FMS−, N=13) comorbid depression and in 17 healthy women. Thermal pain thresholds (TPT) and pain responses were assessed outside the scanner. We compared the discriminative capacity, i.e. the individual׳s capacity to discriminate between lower and higher pain intensities and the response criterion, i.e. the subject׳s tendency to report pain during noxious stimulation due to psychological factors. [11C] raclopride binding potential (BP), defined as the ratio of specifically bound non-displaceable radioligand at equilibrium (BPND) was used as measure of D2/D3 receptor availability. We found significant group effects of BPND in striatal regions (left ventral striatum, left caudate nucleus and left nucleus accumbens) between FMS+ and FMS− compared to healthy subjects. Correlational analysis showed negative associations between TPT and D2/D3 receptor availability in the left caudate nucleus in FMS-, between TPT and D2/D3 receptor availability in the right caudate nucleus in FMS + and positive associations between TPT and D2/D3 receptor availability in the left putamen and right caudate nucleus in healthy controls. The response criterion was positively associated with D2/D3 receptor availability in the right nucleus accumbens in FMS − and negatively with D2/D3 receptor availability in the left caudate nucleus in healthy controls. Finally, no significant associations between D2/D3 receptor availability and discriminative capacity in any of the groups or regions were determined. These findings provide further support for a disruption of dopaminergic neurotransmission in FMS and implicate DA as important neurochemical moderator of differences in pain perception in FMS patients with and without co-morbid depression.

Relation of Serum Testosterone Levels to High Density Lipoprotein Cholesterol and Triglyceride in Men

PP-243 Low HDL cholesterol (HDL-C) levels are now recognized as an independent cardiovascular risk factor and comprise part of the metabolic syndrome. Low testosterone (T) levels are a common finding in men with coronary artery disease. The relationship between endogenous plasma testosterone and

Associations of endogenous testosterone and lipid profiles in middle-aged to older Taiwanese men

The relationship between endogenous plasma testosterone and plasma lipids was assessed among 856 Taiwanese men ≧40 years old originally recruited for an epidemiological study of testosterone deficiency syndrome. Blood samples were drawn from fasting (n = 562) and non-fasting (n = 294) subjects between 0800 to 1100 hours. With adjustment of age, body mass index and sex hormone-binding globulin, the following results were shown: (i) triglyceride (TG) levels were negatively associated with quartile levels of testosterone, and the magnitudes of associations were greater for postprandial TGs than for fasting TGs; (ii) high-density lipoprotein cholesterol (HDL-C) levels were positively related to quartile levels of testosterone, but the associations became insignificant after further control of TGs; and (iii) the calculated low-density lipoprotein cholesterol (LDL-C) levels were positively associated with quartile levels of testosterone. Similar results were obtained in multivariate linear regression analyses with additional control of hypertension and diabetes. In these Taiwanese men, the favorable association of endogenous plasma testosterone with HDL-C counterbalances the unfavorable association of it with LDL-C, while the net influence of testosterone on plasma lipids for cardiovascular system was still in the beneficial direction due to its negative association with postprandial plasma TG levels.

Endogenous plasma testosterone levels and commission errors in women: A preliminary report

A correlation between elevated testosterone and aggressive behavior has been demonstrated in animals and to a lesser degree in humans, primarily in the context of dominance. Some aggression, namely non-premeditated aggression, is characterized by impaired impulse control. Real-world aggressive histories and self-reported impulsivity have correlated with commission errors (failures to withhold responses to nontarget stimuli) in versions of the continuous performance test (CPT). To begin exploring whether testosterone may play a role in aggression due more to a direct relationship with impaired impulse control, we related plasma total testosterone concentrations of 27 psychiatrically healthy women to commission errors in two variants of the CPT — with and without interstimulus distracters. Controlling for age and IQ, testosterone did not relate to rates of correct detections in either task, but correlated positively with commission errors in the distracter CPT variant. In light of the fact previous studies find commission errors on the CPT are associated with impulsivity, the results of this study support a positive relationship between testosterone and impulsivity.

The effects of cortisol and testosterone on renal function in male Antechinus stuartii (Marsupialia).

Seasonal changes in the physiology of Antechinus stuartii result in complete male mortality after mating. The most important endocrine changes in males are large rises in plasma testosterone and cortisol concentrations. Glomerular filtration rate (GFR) in males declines coincident with high plasma testosterone and cortisol. In the present study GFRs were measured in males captured in May (when endogenous plasma testosterone and cortisol levels are low) and given depot injections of either saline, testosterone-only, cortisol-only or testosterone plus cortisol at doses designed to mimic plasma levels during the mating period. GFR decreased significantly with testosterone injection, independent of cortisol treatment. Urinary concentrations of sodium and chloride, and osmolality decreased significantly with cortisol treatment, although the addition of testosterone reversed the effect. Total urinary excretion of electrolytes was similar between groups. Plasma potassium levels significantly increased in testosterone plus cortisol treated males. Plasma sodium levels significantly increased and plasma chloride significantly decreased in all groups treated with cortisol. Water consumption significantly increased in all cortisol-treated males and food consumption significantly increased in all testosterone-treated males. The seasonal renal functional changes observed in A. stuartii were mimicked by testosterone administration.

Testosterone and the Circadian System of the Male Canary (Serinus canaria)

Effects of exogenous testosterone on the circadian system of the male domestic canary (Serinus canaria) were studied in light:dark (L:D) cycles with 16 h of bright light (ca. 35 lx) and 8 h of dim light (ca. 3.0 lx) during the nonreproductive (regressive)phase of the annual gonadal cycle. In addition, effects of testosterone implants were tested under L:D cycles (35:3.0 lx) with different L:D ratios and periods (T> 24 h). The question was asked whether male sex hormones affect entrainment properties of the circadian pacemaker system and whether they differentially influence circadian parameters of various behavioral functions (e.g., perch hopping, feeding, vocalization). During the regressive phase, at low levels of endogenous plasma testosterone, application of exogenous testosterone increased locomotor and vocalization (songs and calls) to the levels measured previously during the reproductive (progressive)phase. Differential effects of testosterone on amount and activity time (α) of perch ho...

Psychological and Behavioural Effects of Endogenous Testosterone Levels and Anabolic-Androgenic Steroids Among Males

The psychological and behavioural effects of endogenous testosterone levels and anabolic-androgenic steroids in males have been investigated for over 50 years in both clinical and nonmedical uses, including the influence of anabolic-androgenic steroids on the nervous system and neuromuscular expression as a mechanism for behavioural and ergogenic effects. The relationship between moods, behaviour and endogenous plasma testosterone levels, as well as anabolic steroids and corticosteroid administration has been studied, including psychological dependence, withdrawal effects, and major methodological issues. While a relationship between endogenous testosterone levels and aggressive behaviour has been observed in various animal species, it is less consistent in humans. It can be concluded that, although the use of exogenous anabolic-androgenic steroids may have psychological and behavioural effects in some patients and athletes, the effects are variable, transient upon discontinuation of the drugs, and appear to be related to type (17 alpha-alkalated rather than 17 beta-esterified), but not dose, of anabolic-androgenic steroids administered. The roles of genetic factors, medical history, environmental and peer influences, and individual expectations are likewise unclear. In general, the evidence at present is limited and much additional research will be necessary for a complete understanding of this relationship.

ENDOGENOUS SEX HORMONE LEVELS IN OLDER ADULT MEN WITH DIABETES MELLITUS

In a Southern California population-based cohort of 985 men aged 40-79 years in 1972-1974, 110 men with diabetes had significantly lower mean levels of endogenous plasma testosterone and sex hormone-binding globulin than did 875 nondiabetic men. Mean androstenedione, estrone, and estradiol levels did not differ significantly by diabetic status. The testosterone and sex hormone-binding globulin differences were reduced but not eliminated after adjustment for age and body mass index (weight (kg)/height (m)2). Twenty-one percent of diabetic men compared with 13% of nondiabetic men had testosterone levels below a categorically defined normal level of 3,500 pg/ml. Testosterone was inversely related to degree of glycemia in the whole cohort. Throughout the whole range of plasma glucose, there was a stepwise decrease in mean testosterone levels per categorical increase in fasting plasma glucose, apparent in both diabetics and nondiabetics. The clinical and physiologic implications of the reduced testosterone levels in diabetic men merit further investigation.

Comparisons of the Nuclear Uptake of [<sup>3</sup>H]-Testosterone and Its Metabolites by the Brains of Male and Female Macaque Fetuses at 122 Days of Gestation

Testosterone secreted by the testis of the macaque fetus is thought to influence certain aspects of the brain's subsequent development which may be responsible for the ontogeny of sexually dimorphic patterns of behavior. To compare the interactions between testosterone and the receptors for androgens and estrogens in brain cell nuclei in the two sexes, 7 intact female fetuses and 5 intact male fetuses were injected in utero at about 120 days of gestation with [3H]-testosterone (250 microCi i.v. or 500 microCi s.c.). One hour later, fetuses were delivered by cesarean section, and samples of brain and peripheral tissues were homogenized and separated into purified nuclear and supernatant fractions. Fractions were analyzed by high performance liquid chromatography to measure levels of [3H]-testosterone and its metabolites. Concentrations of radioactivity extracted from cell nuclei were significantly higher in the hypothalamus-preoptic area than in other brain areas (p less than 0.001); [3H]-estradiol represented 65.0 +/- 5.7% of this radioactivity and nuclear concentrations of this metabolite were 73% lower in males than in females (p less than 0.001). Nuclear concentrations of [3H]-testosterone in the pituitary gland (68.9 +/- 8.8% of extracted radioactivity) were 48% lower in males than in females (p less than 0.001). There was no evidence of a sex difference in the tissue uptake of radioactive steroids from blood, but in males, levels of endogenous plasma testosterone (599.8 +/- 208.2 ng/100 ml) were significantly higher than in females (37.7 +/- 28.5 ng/100 ml; p less than 0.01), and the specific activity of [3H]-testosterone in blood was consequently lower in males than in females.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute suppression of endogenous teststterone levels by exogenous testosterone in normal men

The effect of exogenous testosterone on endogenous plasma testosterone was studied in normal men. Intramuscularly administered testosterone-19, 19, 19-d 3 rapidly appeared in the systemic circulation in large amounts. Endogenous plasma testosterone was suppressed to near-castrate levels. The suppressed level began to rise between 6 and 10 h, and reached a preinjection level at 24 h after the injection. Plasma LH decreased with a concomitant decrease in endogenous testosterone and began to rise as soon as plasma total testosterone returned to physiological levels.