Seasonal Changes of Serum Gonadotropins and Testosterone in Men Revealed by a Large Data Set of Real-World Observations Over Nine Years

Abstract

Environmental rhythmicity is able to affect the hypothalamic-pituitary-gonadal axis in several animals to achieve reproductive advantages. However, conflicting results were obtained when assessing the environmental-dependent rhythmicity on reproductive hormone secretion in humans. This study was designed to evaluate seasonal fluctuations of the main hormones involved in the hypothalamic-pituitary-gonadal axis in men, using a big data approach. An observational, retrospective, big data trial was carried out, including all testosterone, luteinizing hormone (LH) and follicle-stimulating hormone (FSH) measurements performed in a single laboratory between January 2010 and January 2019 using Chemiluminescent Microparticle Immunoassay. Subjects presenting any factor interfering with the hypothalamic-pituitary-gonadal axis were excluded. The trend and seasonal distributions were analyzed using autoregressive integrated moving average (ARIMA) models. A total of 12,033 data, accounting for 7,491 men (mean age 47.46 ± 13.51 years, range 18-91 years) were included. Testosterone serum levels (mean 5.34 ± 2.06 ng/dL, range 1.70-15.80 ng/dL) showed a seasonal distribution with higher levels in summer and a direct correlation to environmental temperatures and daylight duration. LH levels (mean 4.64 ± 2.54 IU/L, range 1.00-15.00 IU/L) presented 2 peaks of secretion in autumn and spring, independently from environmental parameters. FSH levels (mean 5.51 ± 3.24 IU/L) did not show any seasonal distribution. A clear seasonal fluctuation of both LH and testosterone was demonstrated in a large cohort of adult men, although a circannual seasonality of hypothalamic-pituitary-gonadal hormones in humans could be not strictly evolutionarily required. Testosterone seasonality seems independent from LH fluctuations, which could be regulated by cyclic central genes expression, and more sensible to environmental temperatures and daylight duration.

Do seasonal variations in ambient temperature, humidity and daylight duration affect semen parameters? A retrospective analysis over eight years

“…Moskovic et al (2012) showed a significant testosterone/estradiol ratio peak in winter in the younger cohort of patients (Moskovic et al, 2012). Santi et al (2020) demonstrated the seasonality of testosterone levels higher in summer, which was correlated to environmental temperatures and daylight duration. LH (luteinising hormone) levels had two peaks of secretion in autumn and spring, while FSH had no seasonal distribution (Santi et al, 2020).…”

“…The spermatogenesis is critically dependent on the actions of follicle‐stimulating hormone (FSH) and androgen (O'Shaughnessy, 2014). Several studies investigated the seasonal variations in hormones (Moskovic et al., 2012; Santi et al., 2020). Moskovic et al.…”

“…Several studies investigated the seasonal variations in hormones (Moskovic et al, 2012;Santi et al, 2020). Moskovic et al (2012) showed a significant testosterone/estradiol ratio peak in winter in the younger cohort of patients (Moskovic et al, 2012).…”

“…The environmental changes, creating a complex circadian (day) and circannual (year) rhythmicity, affect the whole organism, particularly the endocrine glands and the gonads. The hypothalamic–pituitary–gonadal axis is extremely susceptible to circannual rhythmicity, regulating the hormone levels (Santi et al., 2020). One of the most critical functions of annual hormone changes in nature is the optimisation of reproduction timing, thereby ensuring the highest survival chances of the offspring (Henkel et al., 2006; Roenneberg & Aschoff, 1990).…”

“…Unlike other animal species, humans do not necessitate to set a season of fertility and can reproduce throughout the entire year. Although the human is not normally considered a seasonal breeder, many reports demonstrated the seasonal changes in gonadotropins, gonadal hormones and melatonin levels (Bittman, Dempsey, & Karsch, 1983; Bronson, 1995; Moskovic, Eisenberg, & Lipshultz, 2012; Santi et al., 2020). Additionally, some of the epidemiological studies demonstrated seasonal variations in human birth rates (Lam & Miron, 1994; Roenneberg & Aschoff, 1990; Rojansky, Brzezinski, & Schenker, 1992).…”