OestrogenEstrogen · Oestradiol · Estradiol
The principal female sex hormone, also important for bone, brain and vascular health in everyone.
Oestrogen is a family of steroid hormones — oestradiol is the most active — produced mainly by the ovaries, and in smaller amounts by fat tissue and, in men, by the conversion of testosterone through the enzyme aromatase. Men have and need oestrogen too, at much lower concentrations.
It matters far beyond reproduction. Oestrogen restrains the osteoclasts that break down bone, which is why bone loss accelerates sharply after menopause; it influences fat distribution, insulin sensitivity, vascular function, mood and sleep. Its decline in perimenopause explains a cluster of changes that are often misattributed to age alone.
In practice, low oestrogen in menstruating athletes is a warning sign rather than a badge of leanness — it usually signals low energy availability and comes with a real cost to bone. Anyone facing decisions about hormone therapy should be having that conversation with a clinician.
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Written and reviewed by Mathew Beale, MSc Biotechnology, University of Reading.
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