Premenstrual Syndrome (PMS)

Premenstrual syndrome is a cluster of emotional and physical symptoms that appear in the luteal phase — the one to two weeks before a period — and settle within a few days of bleeding starting. The defining feature is not the symptom list but the timing: symptoms must be absent in the follicular phase, which is why prospective daily tracking over two cycles is the diagnostic standard rather than recall. Around 80% of menstruating women notice some premenstrual change, roughly 20-30% have symptoms significant enough to interfere with daily life, and 3-8% meet criteria for premenstrual dysphoric disorder, a severe form dominated by mood symptoms and recognised as a distinct diagnosis. The underlying mechanism is not an abnormal hormone level — hormone concentrations in women with PMS are usually normal. It is an atypical central sensitivity to the normal fall in progesterone and its neuroactive metabolite allopregnanolone, which modulates GABA-A signalling, together with serotonergic changes. Treatment has several evidence-backed routes. SSRIs, taken continuously or only in the luteal phase, are the most effective for mood-dominant PMS and PMDD. Combined oral contraceptives that suppress ovulation help some women. Among supplements, calcium at 1,000-1,200 mg has the best randomised evidence, vitex has repeatedly beaten placebo for overall symptom scores and breast tenderness, and vitamin B6 up to 100 mg has modest support. Regular aerobic exercise, consistent sleep and reduced alcohol contribute reliably.

• •Irritability, anger or a short fuse
• •Low mood, tearfulness or anxiety
• •Breast tenderness and fullness
• •Bloating and fluid retention
• •Headache or migraine
• •Food cravings, especially carbohydrate or chocolate
• •Fatigue and disrupted sleep
• •Difficulty concentrating
• •Acne flare
• •Joint or muscle aches

• •Heightened central sensitivity to the normal luteal fall in progesterone and allopregnanolone
• •Altered serotonergic transmission during the luteal phase
• •Cyclical fluid and sodium shifts driving bloating and breast fullness
• •Genetic predisposition, with strong familial clustering
• •Amplifying factors: chronic stress, poor sleep, low physical activity, high alcohol intake
• •Low dietary calcium and vitamin D intake, associated with higher symptom burden

PMS is a disorder of response, not of hormone level. Ovulation produces the normal luteal rise and then fall in progesterone; in susceptible women the brain's GABA-A receptors respond atypically to the withdrawal of allopregnanolone, and serotonergic tone drops alongside. This explains three otherwise puzzling observations: symptoms disappear in anovulatory cycles and after menopause, SSRIs work within days rather than the weeks needed in depression, and measured hormone levels are indistinguishable from women without symptoms.