Seasonal variation of testosterone and waist to hip ratio in men: the Tromsø study

Lack of seasonal variation in serum sex hormone levels in middle-aged to older men in the Boston area

CONTEXT

Previous studies of seasonal variation of testosterone and other hormones in men have produced mixed results regarding the number and timing of peaks and nadirs and whether hormones vary seasonally at all. Wide variation in study designs, sample sizes, analytical methods, and characteristics of the study populations may account for the heterogeneity of results.

OBJECTIVE

The objective of the study was to determine whether serum total, free, and bioavailable testosterone, dihydrotestosterone, SHBG, LH, dehydroepiandrosterone, dehydroepiandrosterone sulfate, estrone, estradiol, and cortisol vary seasonally in men.

DESIGN

Two blood samples were drawn 1-3 d apart at study entry and again 3 and 6 months later (maximum six samples per subject). Hormone levels 1-3 d apart were averaged to reduce short-term intrasubject variation.

SETTING

The study population consisted of a community-dwelling population (Boston, MA).

STUDY PARTICIPANTS

One hundred thirty-four men 30-79 yr old were randomly selected from the respondents to the Boston Area Community Health Survey. One hundred twenty-one men who completed all six visits were included in the analysis.

MAIN OUTCOME MEASURES

In a repeated-measures analysis, 3-month change in hormone levels, measured twice per subject, and in a sinusoidal nonlinear regression with random subject effects, average hormone level in samples 1-3 d apart were measured.

RESULTS

Aside from cortisol, no evidence of seasonal variation in hormone levels was found. The amplitude of seasonal variation was much smaller than total intraindividual variation for all hormones considered.

CONCLUSIONS

Seasonal variation is likely an unimportant source of variation clinically and in epidemiological studies of hormone levels.

The validity of androgen assays

Problems in the measurement of androgens and in interpreting results have been reviewed and classified as follows: PREANALYTICAL FACTORS: The exact sampling conditions in relation to circadian and seasonal variations, diet, alcohol, physical activity and posture.

PHYSIOLOGICAL AND MEDICAL FACTORS

Androgen levels vary according to the patient's general health, stress, sexual activity and smoking habits. Analytical variables. Sample preservation and storage variables are often unknown. The different androgen assays used have widely differing accuracy and precision and are subject to large inter-laboratory variation, which especially in women and children can render the results of routinely available direct immunoassays meaningless.

INTERPRETATION OF RESULTS

Laboratory reference ranges vary widely, largely independent of methodology, and fail to take into account the log-normal distribution of androgen values, causing errors in clinical diagnosis and treatment. Other unknowns are antagonists such as SHBG, estrogens, catecholamines, cortisol, and anti-androgens. As well as age, androgen receptor polymorphisms play a major role in regulating androgen levels and resistance to their action.

CONCLUSIONS

Though laboratory assays can support a diagnosis of androgen deficiency in men, they should not be used to exclude it. It is suggested that there needs to be greater reliance on the history and clinical features, together with careful evaluation of the symptomatology, and where necessary a therapeutic trial of androgen treatment given.

Seasonal variation in serum concentrations of reproductive hormones and urinary excretion of 6-sulfatoxymelatonin in men living north and south of the Arctic Circle: a longitudinal study

OBJECTIVE

Seasonal variation in photoperiod or temperature may influence human reproductive biology. The present study evaluated whether seasonal changes occurred in the levels of reproductive hormones and the major melatonin metabolite, 6-sulfatoxymelatonin (aMT6s), in populations exposed to extreme variation in photoperiod and temperature.

DESIGN

Two separate cohorts of Norwegian men were recruited from the general population in either of two locations: Tromsø (69.5 degrees N, n = 92) or Oslo (60 degrees N, n = 112), located north and south of the Arctic Circle (66.5 degrees N), respectively.

MEASUREMENTS

Four blood and 12-h overnight urine samples were obtained on separate occasions over a 12-month period, including during the photoperiod maximum and minimum. Serum concentrations of FSH, LH, testosterone (T), oestradiol (E(2)), SHBG and the urinary excretion of aMT6s were assessed.

RESULTS

Statistical analysis using generalized estimating equations indicated that LH levels were lowest during early winter in both locations (both P = 0.01). In Tromsø, free T and E(2) concentrations peaked during early winter (P = 0.02 and 0.003, respectively). In Oslo, free T levels were lowest during early winter (P = 0.06) whereas E(2) levels were lowest during late summer (P < 0.001). Urinary aMT6s concentrations were lowest during early summer in Tromsø and Oslo. Concentrations peaked during early winter in Tromsø (P < 0.001) and during late winter in Oslo (P < 0.001).

CONCLUSIONS

LH levels exhibited similar changes in both locations, whereas the patterns of changes of the sex steroid concentrations differed, possibly indicating different underlying mechanisms. Excretion of aMT6s was lowest during early summer in both locations, indicating that the long natural photoperiod was sufficient to cause suppression of melatonin secretion. Whether these changes have any biological significance remains uncertain.

Androgen deficiency, diabetes, and the metabolic syndrome in men

PURPOSE OF REVIEW

The burden of androgen deficiency in men with diabetes and the metabolic syndrome has become increasingly apparent in population-based studies. This article focuses on the mechanisms underlying the interdependent relationship between these conditions.

RECENT FINDINGS

Various definitions of hypogonadism, the metabolic syndrome and diabetes have been proposed and are used in the literature. Cross-sectional studies have found that between 20 and 64% of men with diabetes have hypogonadism, with higher prevalence rates found in the elderly. Hypogonadism can be a risk factor for the development of diabetes and the metabolic syndrome through various mechanisms including changes in body composition; androgen receptor polymorphisms; glucose transport; and reduced antioxidant effect. Conversely, diabetes and the metabolic syndrome can be risk factors for hypogonadism through some similar but mostly distinct mechanisms, such as increased body weight; decreased sex hormone binding globulin levels; suppression of gonadotrophin release or Leydig cell testosterone production; cytokine-mediated inhibition of testicular steroid production; and increased aromatase activity contributing to relative estrogen excess.

SUMMARY

The relationship between diabetes, the metabolic syndrome and androgen deficiency is complex. Testosterone supplementation, by either oral or intramuscular routes and through exogenous or endogenous delivery, has a promising role in this population although further clinical trials are needed.

Seasonality, waist-to-hip ratio, and salivary testosterone

Patterns of seasonal variation in testosterone (T) and T-dependent measures are poorly understood in humans and particularly in women, despite their importance in other animals. We examined seasonal fluctuations in salivary T in women and men, and waist-to-hip ratio (WHR) in women. Participants were 220 women and 127 men from central and West Coast North America. Results showed that T was significantly highest in autumn for both women and men, and that WHR in women closely matched the seasonal variation in T, with high values in the fall and summer. This suggests that T does show a reliable fluctuation over the seasons, which may result in meaningful fluctuations in behavioral, cognitive, and somatic variables associated with T.

Epidemiology: testosterone and the metabolic syndrome

Low levels of testosterone, hypogonadism, have several common features with the metabolic syndrome. In the Tromsø Study, a population-based health survey, testosterone levels were inversely associated with anthropometrical measurements, and the lowest levels of total and free testosterone were found in men with the most pronounced central obesity. Total testosterone was inversely associated with systolic blood pressure, and men with hypertension had lower levels of both total and free testosterone. Furthermore, men with diabetes had lower testosterone levels compared to men without a history of diabetes, and an inverse association between testosterone levels and glycosylated hemoglobin was found. Thus, there are strong associations between low levels of testosterone and the different components of the metabolic syndrome. In addition, an independent association between low testosterone levels and the metabolic syndrome itself has recently been presented in both cross-sectional and prospective population-based studies. Thus, testosterone may have a protective role in the development of metabolic syndrome and subsequent diabetes mellitus and cardiovascular disease in aging men. However, clinical trials are needed to confirm this assumption.

The influence of season on oxidant–antioxidant status in trained and sedentary subjects

The association between oxidative stress and cardiovascular diseases is a widely accepted fact today. Generally, men have a higher risk of cardiovascular incidents and mortality from acute myocardial infarction and strokes. We have examined sport-associated circannual rhythms of oxidant and antioxidant processes by measuring plasma LPO, erythrocyte SOD, CAT, Gpx activity and plasma hormonal status in both sedentary and long-term trained men and women. We have shown seasonal variations in both oxidant and antioxidant status in all examined groups. The largest difference was observed in the oxidant status between sedentary men and women during autumn and winter, which is considered a period of high coronary risk for men. Sport decreased LPO in trained men in autumn, while the same effect in trained women was shifted towards summer. These data state that regular, long-term physical exercise training induces adaptive responses that confer protection against oxidative stress, as well as the beneficial effect of exercise with regard to season, particularly in men during a period of high coronary risk (autumn and winter, respectively) and in women during summer.

Seasonal variation of sexual abuse in Santiago de Chile

BACKGROUND

Seasonal variations of sexual crime have been seldom studied in the world. Santiago, a city situated at 33 degrees south latitude with a well defined four season climate, has a reliable forensic registry, providing a good opportunity for the assessment of seasonality in this type of crime.

MATERIALS AND METHODS

After studying monthly records of sexual abuse from the registry of the Servicio Médico Legal of Santiago between 1990 and 2001, a ratio of observed to expected monthly frequency was obtained, allowing the assessment of the seasonal character of the phenomenon.

RESULTS

A total number of 11,844 cases of sexual abuse were recorded during 12 years of the study. Statistically significant differences could be demonstrated between spring and autumn, with a peak in November and a nadir in June.

CONCLUSIONS

A distinct seasonal pattern can be set forth for sexual abuse in Santiago, Chile.

Adaptive variation in testosterone levels in response to immune activation: empirical and theoretical perspectives

High testosterone levels reflect investment in male reproductive effort through the ability to produce and maintain muscle tissue and thus augment mate attraction and competitive ability. However, high testosterone levels can also compromise survivorship by increasing risk of prostate cancer, production of oxygen radicals, risk of injury due to hormonally-augmented behaviors such as aggression, violence and risk taking, reduced tissue and organ maintenance, negative energy balance from adipose tissue catabolism, and suppression of immune functions. Here, I briefly discuss how inter- and intra-individual variation in human male testosterone levels is likely an adaptive mechanism that facilitates the allocation of metabolic resources, particularly in response to injury, illness or otherwise immune activation. Maintaining low testosterone levels in resource-limited and/or high pathogen-risk environments may avoid some immunosuppression and suspend energetically-expensive anabolic functions. Augmenting testosterone levels in the presence of fertile and receptive mates, areas of high food resource availability, and low disease risk habitats will function to maximize lifetime reproductive success.

The decline of androgen levels in elderly men and its clinical and therapeutic implications

Aging in men is accompanied by a progressive, but individually variable decline of serum testosterone production, more than 20% of healthy men over 60 yr of age presenting with serum levels below the range for young men. Albeit the clinical picture of aging in men is reminiscent of that of hypogonadism in young men and decreased testosterone production appears to play a role in part of these clinical changes in at least some elderly men, the clinical relevancy of the age-related decline in sex steroid levels in men has not been unequivocally established. In fact, minimal androgen requirements for elderly men remain poorly defined and are likely to vary between individuals. Consequently, borderline androgen deficiency cannot be reliably diagnosed in the elderly, and strict differentiation between "substitutive" and "pharmacological" androgen administration is not possible. To date, only a few hundred elderly men have received androgen therapy in the setting of a randomized, controlled study, and many of these men were not androgen deficient. Most consistent effects of treatment have been on body composition, but to date there is no evidence-based documentation of clinical benefits of androgen administration to elderly men with normal or moderately low serum testosterone in terms of diminished morbidity or of improved survival or quality of life. Until the long-term risk-benefit ratio for androgen administration to elderly is established in adequately powered trials of longer duration, androgen administration to elderly men should be reserved for the minority of elderly men who have both clear clinical symptoms of hypogonadism and frankly low serum testosterone levels.

No major month to month variation in free testosterone levels in aging males. Minor impact on the biological diagnosis of 'andropause'

BACKGROUND

The measurement of bioavailable testosterone (BT) or free testosterone (FT) levels is currently considered the gold standard for the diagnosis of androgen deficiency in elderly men. While the impact of age on circulating testosterone levels (total, bioavailable and free) has been strongly documented, the existence of seasonal variations in testosterone levels remains debated.

OBJECTIVE

We investigated whether seasonal variations in serum calculated free testosterone (cFT) levels may translate into variations in the prevalence of low testosterone levels. Diagnosis was on the basis of biochemical determinations and was cross-checked with the prevalence of clinical signs and symptoms of 'andropause', as assessed by the Androgen Deficiency in Aging Males (ADAM) questionnaire.

METHODS

The study recruited 5028 men aged 50 years and over from September 2000 to January 2003. Their serum FT levels were assessed and they completed the French ADAM test. Men were considered eugonadal when cFT was > or =70 ng/l. The ADAM test was scored as described originally. The prevalence of 'andropause', diagnosed by the two methods, was compared throughout the year, on a month by month basis.

RESULTS

The percentage of subjects with cFT levels below 70 ng/l increased significantly with age (P<0.001). Serum cFT levels (mean [SD]) varied significantly with the month of sampling (P<0.0001), the highest (88.1 [30.2] ng/l) and lowest (76.9 [28.0] ng/l) mean values occurring in April and in October, respectively. Conversely, the prevalence of testosterone deficiency (cFT<70 ng/l) reached a peak in October (45.7%) and a nadir in April (29.7%). Although the prevalence of 'andropause', based on the ADAM questionnaire, increased significantly with age (P<0.0001), no influence of the month of the year was noticed.

CONCLUSIONS

Our results confirm a progressive age-related decline in FT levels. The monthly variations in serum FT values, observed throughout the year, do not show a major seasonal rhythm in elderly community-dwelling males, since the magnitude of the variations (<15%) remains marginal. This slight variation may, however, have an impact on the number of elderly men diagnosed with Partial Androgen Deficiency in Aging Males (PADAM).

The Role of Alcohol and Steroid Hormones in Human Aggression

The association between alcohol and aggressive behavior is well established although a direct causal relationship has proven hard to demonstrate. There are, however, indications that alcohol facilitates aggression in individuals who already have a predisposition to behave aggressively. Aggressive personality disorders have in turn been explained by elevated testosterone level. A one-to-one relation between increased levels of testosterone and aggression has been, nevertheless, difficult to reveal. Two metabolites of testosterone, estradiol and 5alpha-dihydrotestosterone (DHT), have been studied much less in human aggressive behavior. Estradiol might reduce androgenic effects and have a counterbalancing influence on aggression. DHT, again, has a much higher affinity than testosterone to androgen receptors, and there are indications that some of the effects of testosterone-mediating aggressive behavior occur after aromatization. Disregard of seasonal and circadian fluctuations in male testosterone production might be responsible for some of the inconclusive testosterone-aggression results. In addition, increasing age decreases both aggressive behavior and testosterone production in males. Cortisol has yielded conflicting results as a mediator in aggressive behavior. Both higher and lower levels have been reported in aggressive and abusive men. Finally, the acute and chronic effects of alcohol influence the steroid hormone levels in various ways. The present understanding of the etiology of aggression is still vague. It is clear that a multidimensional approach, combining both biological and psychosocial factors, will be necessary for the development of a more general concept of human aggression in the future.

Reproductive function during summer and winter in Norwegian men living north and south of the Arctic circle

Seasonal, daylight-dependent variation in human spermatozoa counts, with lowest values during summer, has been suggested. To test this hypothesis, we performed a longitudinal study of semen quality and reproductive hormone levels in Norwegian men living north and south of the Arctic Circle. An ejaculate and a serum specimen were obtained both in summer and in winter from 92 volunteers in Tromsoe (69 degrees north latitude) and 112 in Oslo (60 degrees north latitude). Semen analyses were performed, and serum was assayed for FSH and inhibin B. The median spermatozoa concentration in Tromsoe after adjustment for abstinence period length was 49 x 10(6)/ml in summer and 54 x 10(6)/ml in winter. Corresponding values for Oslo were 59 x 10(6)/ml and 54 x 10(6)/ml. The seasonal differences in spermatozoa concentration were not statistically significant, nor were significant differences observed in median total spermatozoa count, semen volume, percentage progressive motile spermatozoa, or FSH. In Tromsoe, but not Oslo, inhibin B concentration was slightly, but significantly (P = 0.02) higher in winter than summer (229 ng/liter vs. 223 ng/liter). The length of the daylight period may have a slight impact on hormonal markers of spermatogenesis but does not cause substantial changes in spermatozoa numbers and motility.

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

We have previously reported seasonal variations in both total and free testosterone in men living in north Norway. The aim of this cross-sectional study was to determine whether seasonal variation in testosterone also occurs in men living in geographical areas with less extreme seasonal variation in sunlight and temperature. In 915 men aged 24-91 years from Rancho Bernardo, a suburb of San Diego in southern California, we found that neither total nor bioavailable testosterone varied by season, with or without adjustments for age and anthropometric measurements. Of all examined covariates, only physical activity showed a seasonal variation, with a peak in August (p < 0.001), and adjusting for physical activity did not change the lack of seasonal variation in testosterone. In addition, there was no association between testosterone and mean air temperature, or testosterone and possible hours of sunshine. We conclude that men living in southern California show no seasonal variation in testosterone levels. One possible explanation, besides the difference in climate, for the diverging findings between our previous study and the present study is different sleep patterns.

[Testosterone deficiency and the problem of normal values]

If a testosterone deficiency is demonstrated, the exact cause of the endocrine hypogonadism should be determined by appropriate endocrinological, imaging and other andrological diagnostic techniques, as such a deficiency can be the result of various illnesses. At present there are no satisfactory evidence based, generally accepted norms for testosterone levels recognised for the aging male. Laboratory analysis of testosterone must be carried out taking into consideration the physiological variability using methods validated in house, with strict internal and external quality control. For the diagnosis of reduced testosterone levels, satisfactorily established own normal values for the technique used are recommended.

Time trends (1993–1997) and seasonal variation in body mass index and waist circumference in the Netherlands

OBJECTIVE

To compare the time trend and seasonal variation in body mass index (BMI) and waist circumference.

DESIGN

Continuous monitoring health survey carried out between 1 June 1993 and 31 May 1997.

SUBJECTS

A total of 8,186 men and 9,638 women aged 20-59 y from three towns in the Netherlands.

MEASUREMENTS

BMI and waist circumference. Obesity was defined as BMI > or =30 kg/m(2), abdominal obesity as waist circumference > or =102 cm for men and > or =88 cm for women.

RESULTS

Levels of BMI and waist circumference increased between 1 June 1993 and 31 May 1997. Among women, the time trend in abdominal obesity was stronger than that in obesity. Further, levels of BMI and waist circumference were higher in winter than in summer seasons. The seasonal variation was larger for abdominal obesity than for obesity, among both men and women.

CONCLUSIONS

The time trend in women and the seasonal differences in both men and women were stronger for abdominal obesity than for obesity. Surveys on BMI and waist circumference are only comparable if season is taken into account. Furthermore, the waist circumference is a more sensitive indicator of variations in lifestyle and body composition than is body mass index.

The endocrine pharmacology of testosterone therapy in men

The review starts off by outlining the history of the discovery of the male sex hormone testosterone and the historical background to the various, often dubious, approaches to the treatment of age-related endocrine disorders in older men. A discussion of congenital androgen deficiency in young men is followed by methods of diagnosing hypogonadism in older men. Among therapeutic options, the alternatives to direct testosterone replacement are discussed, although none of them have proved to be particularly successful in clinical practice. For testosterone replacement itself, various routes of administration and pharmaceutical formulations are now available, facilitating good monitoring and individualized therapy.

Epidemiology of type 1 and type 2 diabetes. The added value of diabetes registries for conducting clinical studies: the Belgian paradigm

Diabetes registries have documented that the lifetime risk of diabetes amounts to at least 10% in the western world. Moreover the prevalence of type 2 diabetes is increasing worldwide especially in developing countries. Furthermore there is a secular trend toward earlier clinical manifestation of both type 1 and type 2 diabetes. In the absence of a permanent cure for primary diabetes the present estimated number of at least 150 million diabetic patients worldwide is expected to double within the next 20 years. Consequently a sharp increase in the global burden of chronic diabetes complications is to be feared in the coming decades. Therefore it is absolutely mandatory to intensify research efforts aiming at identifying the etiological factors involved and designing effective strategies for prediction and prevention of the disease and its devastating complications. Diabetes registries constitute instruments of choice to conduct such studies because they are able to collect standardised clinical, demographic and biological information from sufficiently large representative groups of patients and risk groups such as first degree relatives. Since 1989, the Belgian Diabetes Registry is studying all types of diabetes presenting before age 40 in Belgium and provides a paradigm of how diabetes registries may also contribute to the advancement of knowledge on disease heterogeneity, etiology, prediction and prevention.