Could seasonal variation in testosterone levels in men be related to sleep?

Is vitamin D status reflected by testosterone concentration in elite athletes?

Vitamin D is a nutrient whose active form affects tissues as a hormone and possibly enhances performance. One plausible mechanism is by increasing testosterone concentration, which is established as an important factor for athletic performance. Therefore the aim of the study was to examine the relationship between plasma concentration of 25(OH)D and testosterone in Polish elite track and field athletes depending on vitamin D status, season, training period, body composition, sex, type of training, sun exposure and vitamin D supplementation. Plasma concentrations of 25(OH)D and testosterone were measured in all seasons within two years in athletes (70 females, 79 males) who represent strength (n = 103) and endurance (n = 46) kinds of sports, in the preparatorycompetitive season and transition period. There were no differences in 25(OH)D concentration between male and female athletes, insufficiency [25(OH)D < 30 ng/ml] was observed in 32.9%, whereas deficiency [25(OH)D < 20 ng/ ml] in 3.2%. Circannual rhythm was noted for vitamin D but not for testosterone concentration; no correlations between them were found either in strength or endurance athletes or between 25(OH)D and body composition. Testosterone concentration was higher in the transition period than in the preparatory-competition period only in male athletes. Higher 25(OH)D was observed in athletes who trained during winter in Africa (higher sun exposure) or used oral supplementation, whereas the respective testosterone levels were unchanged. In athletes, testosterone concentration did not reflect vitamin D status. The widespread of inadequate vitamin D status among athletes, makes it vital to recommend them the regular monitoring of 25(OH)D concentration and use of reasonable supplementation.

Effects of seasonal differences in testosterone and cortisol levels on pain responses under resting and anxiety conditions

PURPOSE

This study investigated whether hormones and pain perception are associated with exam anxiety, and also whether exam anxiety is affected by seasonal differences in testosterone and cortisol levels.

MATERIALS AND METHODS

Forty-six healthy males were recruited from a medical college. Anxiety was induced by having participants perform the Objective Structured Clinical Examination. Pressure was applied to the participants to induce pain. Pain thresholds, pain ratings, anxiety ratings, blood pressure, heart rate, salivary testosterone and cortisol levels were measured under resting and anxiety conditions in the spring and summer. Data were collected from 46 participants during the spring (n=25) and summer (n=21).

RESULTS

Pain thresholds and testosterone levels were significantly lower under anxiety than at rest for all participants (n=46), while cortisol levels, pain ratings, and anxiety ratings were significantly higher under anxiety than at rest. In the spring (n=25), testosterone levels were significantly higher at rest than under anxiety, while there was no difference in cortisol levels between resting and anxiety conditions. In the summer (n=21), cortisol levels were significantly higher under anxiety than at rest, while there was no difference in testosterone levels between resting and anxiety conditions. There were no significant seasonal differences in pain and anxiety ratings and pain threshold.

CONCLUSION

These results indicate that seasonal differences in testosterone and cortisol levels under anxiety and at rest may affect pain responses. These results also suggest that acute clinical pain may be relieved by managing anxiety that is related to a decrease of testosterone in spring and a large increase of cortisol in summer.

Seasonal variations of plasma gonadotropin, prolactin, and testosterone levels in primary and secondary hypogonadism: evidence for an independent testicular role

BACKGROUND

Seasonal hormonal rhythmicity of the hypothalamic-pituitary-gonadal axis may influence reproductive and sexual activity in mammals.

AIM

To investigate whether pituitary-gonadal axis secretion seasonality occurs in men with primary and secondary hypogonadism and whether a hierarchical machinery regulates these variations.

SUBJECTS AND METHODS

Six adult males with Klinefelter's syndrome (KS), eight with idiopathic normosmic hypogonadotropic hypogonadism (HH) and ten sex- and age-matched healthy controls were studied longitudinally for one year. Every three months, three plasma samples for assay of testosterone, LH, FSH, and prolactin were drawn and the mean value was used for statistical analysis.

RESULTS

Healthy males showed a significant seasonality in LH (zenith in spring) and testosterone (zenith in autumn) but not in FSH and prolactin concentrations. Patients with KS and those with HH showed a seasonal rhythmicity only of testosterone values, even if with small amplitude, with the zenith in spring and summer respectively.

CONCLUSION

The lack of dependence of testosterone on gonadotropin variations in normal men and the persistence of seasonal testosterone but not gonadotropin variations both in primary and secondary hypogonadism seem to indicate a possible independent testicular regulation of this seasonality. The shift of testosterone peak in hypogonadal men with respect to controls suggests that LH variations could play a synchronizing, rather than pace-making, role in seasonal testosterone variations. Since hormonal seasonality may also influence gonadal activity in humans, replacement therapy in hypogonadism should be aimed also at restoring a normal seasonal rhythmicity of pituitary-gonadal hormone concentrations.

The evidence for seasonal variations of testosterone in men

Ample evidence exists to support the concept of diurnal variations in testosterone levels; however, substantiation for seasonal fluctuations is sparse and inconsistent. Since circadian disparities exist, laboratory screening for hypogonadism has traditionally been conducted using serum testosterone levels obtained in the early morning. Should circannual variability of testosterone be confirmed, it would make the monitoring of testosterone levels more difficult while forcing the development of seasonal reference standards to allow for comparison. Moreover, decisions to begin treatment and adjustment of practice patterns would likely follow. This review thoroughly explores all of the available evidence concerning seasonal variations in testosterone levels. The impacts of melatonin, vitamin D, sleep-wake cycles, light exposure, physical activity, BMI, and waist circumference are also discussed. Current research suggests that while some evidence exists to support the notion of seasonal testosterone variations, the discussed inconsistencies preclude the incorporation of this concept into current clinical standards.

Seasonal and circadian variation in salivary testosterone in rural Bolivian men

Testosterone (T) plays a key role in the increase and maintenance of muscle mass and bone density in adult men. Life history theory predicts that environmental stress may prompt a reallocation of such investments to those functions critical to survival. We tested this hypothesis in two studies of rural Bolivian adult men by comparing free T levels and circadian rhythms during late winter, which is especially severe, to those in less arduous seasons. For each pair of salivary T(AM)/T(PM) samples (collected in a approximately 12-h period), circadian rhythm was considered classic (C(CLASSIC)) if T(AM) > 110%T(PM), reverse (C(REVERSE)) if T(PM) > 110%T(AM), and flat (C(FLAT)) otherwise. We tested the hypotheses that mean T(AM) > mean T(PM) and that mean T(LW) < mean T(OTHER) (LW = late winter, OTHER = other seasons). In Study A, of 115 T(PM)-T(AM) pairs, 51% = C(CLASSIC), 39% = C(REVERSE), 10% = C(FLAT); in Study B, of 184 T(AM)-T(PM) pairs, 55% = C(CLASSIC), 33% = C(REVERSE), 12% = C(FLAT). Based on fitting linear mixed models, in both studies T(OTHER-AM) > T(OTHER-PM) (A: P = 0.035, B: P = 0.0005) and T(OTHER-AM) > T(LW-AM) (A: P = 0.054, B: P = 0.007); T(PM) did not vary seasonally, and T diurnality was not significant during late winter. T diurnality varied substantially between days within an individual, between individuals and between seasons, but neither T levels nor diurnality varied with age. These patterns may reflect the seasonally varying but unscheduled, life-long, strenuous physical labor that typifies many non-industrialized economies. These results also suggest that single morning samples may substantially underestimate peak circulating T for an individual and, most importantly, that exogenous signals may moderate diurnality and the trajectory of age-related change in the male gonadal axis.

Age-related changes in testosterone and SHBG among Turkana males

To determine age-related changes in biologically available testosterone (T) among men in a subsistence society and their relationship to energetic status, T, sex hormone binding globulin (SHBG) and anthropometric measures were compared among nomadic and settled Turkana pastoralists of northern Kenya. Hormonal measures were available for 104 nomadic men and 72 settled men, estimated ages 20-90 years. Comparison of the two subpopulations revealed significantly higher blood T (32.7+/- 15.1 vs. 23.4+/-15.2 nM) and SHBG (53.8+/- 19.5 vs. 39.7+/- 20.nM) but not free testosterone index (FTI) (65.6+/- 39.3 vs.66.3+/- 45.9) among the nomads. Total blood T did not exhibit a significant linear decline with age in either subgroup, while SHBG values showed a significant linear increase among the nomads. When controlled for energetic status, FTI showed a significant decrease with age among the nomads, but not the settled males. Total blood T was negatively associated with waist circumference among the nomads, but not the settled males. FTI showed a marginally significant negative association with waist circumference, suprailiac skinfold, and % body fat among the nomads but no associations with body composition among the settled group. These results add additional evidence that T is related to energetic status under conditions of negative energy balance and suggest that cross-population variation in the slope of age-related declines in free serum T and salivary T may be related to energetic status through the effects of SHBG.