Figure - available from: International Journal of Endocrinology
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Monthly variations in total and bioavailable testosterone levels in a cohort of men aged 20–70.
Source publication
Objectives:
The aim of the study was to evaluate in a large cohort of males with a wide range of age, metabolic status, and coexistent morbidities whether month of blood test performance was associated with total and bioavailable testosterone levels independent of age, body mass index (BMI), existing cardiovascular disease (CVD), and CVD risk fact...
Citations
... Several studies have reported possible peaks and troughs across seasons. [12][13][14][15] Both Dabbs and Lee showed a peak of testosterone levels in winter, while Ballatsella et al and Zornitski et al reported that testosterone peaks in summer. Conversely, other studies concluded that there are no seasonal variations in testosterone. ...
... Previous studies have demonstrated conflicting results, with some reporting variability having peaks of testosterone in warmer months and some having their testosterone peaks in colder months [12][13][14][15]19,20 while others report no discernable variation from season to season. 16,17,21,22 Although these studies have reported statistically significant differences in testosterone levels by season, this does not necessarily indicate clinical significance. ...
... of testosterone levels in the summer months of 5.44 ng/mL, with a trough in autumn where they found testosterone declined to an average of 5.26 ng/mL.S 19 Another large study by Zornitzki found a difference between peak and trough of 1 nmol/L. 15 Interestingly, our study did show a statistically significant difference in mean total testosterone concentrations between Miami and Pittsburgh. This is unusual in that there has long been a negative association between testosterone levels and age, the cohort of patients in Miami, despite being 7 years older on average, also had higher average levels of testosterone. ...
Introduction
Variation in testosterone levels by season and month have been reported, however results have been inconsistent across studies. Large series are conflicting with reported peaks in June, October, December, and January. Testosterone levels in most of these studies nadir in the spring. The etiology for the variability remains unknown but is likely multifactorial including sunlight exposure, sleep duration, and outdoor temperature.
Objective
To determine if there is seasonal variability in testosterone levels in a large cohort of men and if this variability may be clinically relevant.
Methods
Using a single institutional database, testosterone levels were obtained for men ages 18-99 from 2010-2021 who had at least 2 testosterone levels drawn within a 2-year period. Patients who were currently or previously on exogenous testosterone, testosterone stimulating medications, testosterone suppressing medications, and aromatase inhibitors were excluded from the study. Climate data including mean monthly temperature for Miami-Dade County, FL was obtained from the PRISM Climate Group. Minutes of daylight on the fifteenth day of each month was applied as the representative daylight duration for each month.
Results
There were 3,377 total patients included in the study, there were 9495 total testosterone levels measured with all patients having 2 or more levels. The mean age was 58.8 years old. In the winter the mean testosterone level in the was 422 ng/dl (Figure 1.), the average time of daylight was 682 minutes, and the average temperature was 68 F. In the spring the mean testosterone level was 412 ng/dl, the average time of daylight was 801 minutes, and the average temperature was 78.4 F. In the summer the mean testosterone level was 416 ng/dl, the average time of daylight was 780 minutes, and the average temperature was 83.6 F. In the fall the mean testosterone level in the fall was 417ng/dl, the average time of daylight was 661 minutes, and the average temperature was 75.3 F.
Conclusions
Our findings suggest seasonal variability in testosterone levels with the highest testosterone levels in the winter, the lowest levels in the spring and a steady increase in testosterone levels in the summer and fall. However, this variation is minor and not likely to be clinically relevant.
Disclosure
Any of the authors act as a consultant, employee or shareholder of an industry for: Acerus Pharmaceuticals Consultant, Grant Recipient Boston Scientific Consultant, Grant Recipient Coloplas tConsultant, Grant Recipient Endo Pharmaceuticals Consultant, Grant Recipient Empower Pharmacy Grant Recipient Nestle Health Consultant Olympus Grant Recipient Hims, Inc Advisory Board.
Objective
Seasonal variations in testosterone levels have been reported in some studies, but the results are inconsistent. In this study, we aimed to determine if clinically relevant seasonal variability in testosterone levels exists using a large cohort of men from 2 different institutions, 1 located in an area with seasons (Pittsburgh, Pa) and 1 without seasons (Miami, Fla).
Methods
Using 2 institutional databases, testosterone levels were obtained for men ages 18-99 from 2010 to 2021 who had at least 2 morning testosterone levels drawn within a 2-year period. All samples were analyzed with liquid chromatography with tandem mass spectrometry. To avoid potential confounding by testosterone altering medications patients who were currently or previously on exogenous testosterone, endogenous testosterone-stimulating medications, testosterone-suppressing medications, and aromatase inhibitors were excluded from the study.
Results
There were 9495 and 16 171 total testosterone levels measured from Miami and Pittsburgh, respectively, with all men having 2 or more levels. There was no statistically significant variation in testosterone levels for the overall cohort in Pittsburgh or Miami, respectively. Additionally, when stratified by age group, no individual groups were found to have significant seasonal variability.
Conclusion
Our findings suggest that although there is differing total testosterone levels between men who reside in 2 different climates, there is no significant variability in testosterone levels between seasons. Therefore, testosterone levels can be checked and interpreted without the need to account for the season during which they were drawn.
During mammalian evolution, circulating levels of gonadotropins [i.e., luteinizing hormone (LH) and follicle-stimulating hormone (FSH)] acquired regulation by environmental (e.g., light, temperature, water, food, predators, etc.), and social (e.g., sound, sight, aggression, crowding, etc.) inputs that determine the level of testosterone production and secretion by the testis and systemic levels in the blood. This regulation became coordinated by interaction between the retinohypothalamic-pineal and the hypothalamic-pituitary neural axes, which resulted in androgen levels and its ligand-dependent transducing receptor being the master downstream determinant of male reproduction. A major factor in this selection of androgen levels relates to the unique danger of mammalian reproduction for survival of the individual. During mammalian evolution, breeding needed for survival of the species became episodically (i.e., seasonally) timed by androgen levels. Seasonal breeding has great reproductive advantage in restricting energy requirements for reproduction and limiting dangers associated with procreation (i.e., survival of the species) at the expense of suppression of the flight instinct (i.e., survival of the individual) to the minimal time frame of the breeding season. Human males evolved away from strict seasonal breeding by chronically maintaining androgen levels, enabling human males to reproduce year-round and worldwide, rather than "locking" them into specific indigenous breeding ranges, like other mammals. The price for the reproductive "freedom" that arises from the loss of seasonal breeding is an increased probability of developing prostate cancer as a result of chronically maintaining a hyperplastic state in the prostate. In human males, this results in the loss of episodic pruning of genetically-mutated prostate cancer precursors that normally occurs during seasonal breeding. Instead, the continuous androgen-dependent stimulation of the growth of such precursors occurs during prostate carcinogenesis. This review provides the rationale for the development of a therapeutic approach using PSA-activated prodrugs to selectively deplete prostate-specific AR protein for chemoprevention of prostate cancer.
