What is the physiology of a hot flush

A hot flush is a brain thermostat misfiring: the body suddenly dumps heat through the skin, and the flush is the dumping.

The core mechanism is a cluster of brain cells called KNDy neurons (kisspeptin/neurokinin B/dynorphin). When researchers destroyed these neurons in rats, the animals lost much of their ability to widen skin blood vessels and dump heat, and estrogen's control over body temperature changed [1]. That ties the same neurons to both temperature regulation and the hot flush [1]. Estrogen normally keeps this circuit calm; when estrogen falls, the brake comes off and the thermostat overreacts to tiny temperature changes, triggering a sudden wave of skin vasodilation and sweating. That is the flush.

The rest of the retrieved records are about the hormonal control of reproduction (luteinizing hormone pulses), not the flush itself, so this search does not cover the fuller picture: the exact trigger threshold, why some women get severe flushes and others none, or how the skin vessels and sweat glands are wired downstream. Those layers are outside what these records show.

What the records do show is that the symptom is real and common, and that the popular non-hormonal fixes tested here do not beat placebo: soy isoflavones showed no treatment effect on hot flush frequency [2], omega-3 was no better than placebo [4], and relaxation techniques had insufficient evidence [3]. Hormone therapy is reported as effective first-line treatment [5], though that review is a narrative summary, not a hard-outcome trial, and it flags real risks like blood clots and breast cancer [6].

My call: the physiology is well grounded in animal work, but human mechanistic data and head-to-head treatment trials are thin, so treat any single fix as unproven until it beats placebo in a real trial. Confidence: moderate on the KNDy mechanism, low on which treatment is best for you.