Human hormone seasonality

Abstract

<jats:p>Hormones control the major biological functions of stress response, growth, metabolism and reproduction. In animals these hormones show pronounced seasonality, with different set-points for different seasons. In humans, the seasonality of these hormones remains unclear, due to a lack of datasets large enough to discern common patterns and cover all hormones. Here, we analyze an Israeli health record on 46 million person-years, including millions of hormone blood tests. We find clear seasonal patterns: the effector hormones peak in winter-spring, whereas most of their upstream regulating pituitary hormones peak only months later, in summer. This delay of months is unexpected because known delays in the hormone circuits last hours. We explain the precise delays and amplitudes by proposing and testing a mechanism for the circannual clock: the gland masses grow with a timescale of months due to trophic effects of the hormones, generating a feedback circuit with a natural frequency of about a year that can entrain to the seasons. Thus, humans may show coordinated seasonal set-points with a winter-spring peak in the growth, stress, metabolism and reproduction axes.</jats:p>

Unmasking Seasonal Cycles in Human Fertility: How holiday sex and fertility cycles shape birth seasonality

“…Our results show that although humans have the capacity to reproduce year-round, there is seasonal structuring to our reproductive physiology. Early findings of increased estradiol in the winter (35) have recently been confirmed by a large-scale study (36) that revealed a winter-spring peak in estradiol and testosterone and a summertime peak in luteinizing hormone (LH) and prolactin (36). In addition to seasonal variations in reproductive hormones, humans have seasonal cycles in hormones involved in thermoregulation, metabolism, stress adaptation and growth (36), as well as seasonal changes in the immune system (37,38).…”

Timescales of Human Hair Cortisol Dynamics

“…Karin et al showed that such mass changes are sufficient to explain HPA dysregulation after prolonged stress. (Tendler et al, 2020) proposed that the same model can explain seasonal entrainment of hormones and their seasonal peaks and troughs. Here, we propose that the mass changes provide a ''memory'' to the HPA axis, which can integrate over the fast timescale fluctuations of stress inputs to generate fluctuations that last on the timescale of a year.…”

“…We employ a recently developed model for the HPA axis, which incorporates the effects of the hormones on the total functional mass of hormone-secreting cells (Karin et al, 2020;Tendler et al, 2020). The concentrations of the hormones CRH, ACTH and cortisol are denoted , and .…”

“…Pulse amplitude is largest in the morning, forming a sizable circadian pattern ( Walker et al., 2010 ). Cortisol also has a seasonal rhythm, which peaks in late winter ( Hadlow et al., 2018 ; Miller et al., 2016 ; Tendler et al, 2020 ). The amplitude of this seasonal rhythm is a few percent in temperate clines and rises to tens of percents at high latitudes.…”

Hormone seasonality in medical records suggests circannual endocrine circuits

“…Anonymized data and the source code used to perform the analysis is available at the GitHub repository: https://github.com/alonbar110/Human-hormone-seasonality ( 60 ).…”