Hormones control several biological functions in mammals, including growth, metabolism, reproduction, and responses to stress. However, it is unclear whether human hormones exhibit seasonal patterns, given that detecting such patterns requires hormone measurements.
The researchers analyzed the results of hormone blood tests collected between 2002 and 2017 from almost 3.5 million adults aged 20–80 years and living in Israel. Data came from the medical database of the Israeli health-service Clalit.
The test results demonstrated that human hormones exhibit patterns of seasonality. Effector hormones peaked between winter and spring.
However, most upstream regulating pituitary hormones for growth, reproduction, and stress peaked in late summer. The delay of pituitary hormones was unexpected, given that hormone circuit delays typically last hours rather than months.
By modeling the adrenal and pituitary glands, the authors also determined that gland masses grow within months due to hormones’ trophic effects, producing a feedback circuit with a natural annual frequency.
The findings suggest that hormone seasonality in humans may have a physiological peak season for biological functions, according to the authors.
Hormone seasonality in humans
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