Key Terms

Quick-reference definitions — full context for each appears in the relevant section of the guide.

Amenorrhea

The absence of menstrual periods for three or more months in someone who would otherwise be expected to have them. Causes range from PCOS to stress to low energy availability relative to training demands.

Dysmenorrhea

Painful periods. "Primary" dysmenorrhea occurs without an underlying condition; pain that doesn't respond to appropriately used NSAIDs is worth investigating for an underlying cause like endometriosis.

Endometriosis

A condition in which tissue similar to the uterine lining grows outside the uterus. Commonly diagnosed years after symptom onset due to normalisation of severe menstrual pain.

Perimenopause

The transition period, often lasting several years, before periods stop entirely — marked by increasingly irregular cycles and the onset of symptoms like hot flushes and sleep disruption.

PCOS (Polycystic Ovary Syndrome)

A common hormonal condition, affecting roughly 1 in 10 reproductive-age women, diagnosed via a combination of irregular ovulation, elevated androgens, and/or polycystic-appearing ovaries. Insulin resistance is central to most cases.

Rotterdam Criteria

The internationally endorsed diagnostic framework for PCOS, requiring at least two of three features: irregular ovulation, elevated androgens, and polycystic ovaries on ultrasound.

RED-S (Relative Energy Deficiency in Sport)

A syndrome caused by insufficient energy intake relative to training demands, which can disrupt menstrual function, bone health, immunity, and cardiovascular health — sometimes without obvious weight loss.

Timing Hypothesis

The theory, supported by re-analysis of Women's Health Initiative data, that the risk-benefit balance of hormone replacement therapy depends substantially on how soon after menopause onset it's started.

Vasomotor Symptoms

Hot flushes and night sweats associated with the menopausal transition, which can persist for years for many women.