Fig. 4: Lifespan trajectories of primary sex hormones in humans.

Schematic of mean serum (A) estradiol and (B) testosterone concentrations across five major life stages: infancy/early childhood (0–5 years), pre-puberty (6–11 years), puberty/adolescence (12–17 years), sexual maturity [reproductive years] (18–50 years), and post-menopause/aging (51–80 years). This figure was generated de novo by the authors by extracting and averaging reported values from multiple independent studies^{169,170,171,172,173,174,175,176,177,178} that met the following inclusion criteria: healthy human participants, no use of hormone-modulating medications, and quantitation of total circulating sex steroid levels in serum using mass spectrometry. The elevated sex steroid levels in early childhood cause a “mini-puberty” that kickstarts sex steroid synthesis^28,29. Importantly, circulating hormone levels do not completely reflect their activity in tissues, where many cells can locally produce or convert sex steroids for their own use (intracrine) or for nearby cells (paracrine)¹⁷⁹.