Clinical meaning
Vasomotor symptoms (VMS) — hot flashes and night sweats — are the hallmark clinical manifestation of menopause, affecting approximately 75% of women and significantly impairing quality of life in 25-30%. The pathophysiology centers on dysfunction of the hypothalamic thermoregulatory center caused by estrogen withdrawal. In the arcuate nucleus of the hypothalamus, KNDy neurons (coexpressing kisspeptin, neurokinin B, and dynorphin) modulate the thermoneutral zone — the range of core body temperature within which neither sweating nor shivering is triggered. Estrogen normally suppresses neurokinin B signaling; when estrogen declines, neurokinin B activity increases, dramatically narrowing the thermoneutral zone so that minor fluctuations in core temperature trigger inappropriate heat dissipation responses (cutaneous vasodilation, flushing, diaphoresis). This mechanism is the pharmacological target of NK3 receptor antagonists (fezolinetant). Pharmacotherapy is stratified by mechanism: systemic estrogen therapy (oral or transdermal) directly restores estrogen-mediated suppression of KNDy neuron hyperactivity, providing 50-80% reduction in VMS frequency and is the most effective treatment; transdermal delivery bypasses hepatic first-pass metabolism, avoiding triglyceride elevation and reducing VTE risk compared to oral formulations. SSRIs and SNRIs (paroxetine, venlafaxine) modulate serotonergic and noradrenergic neurotransmission in the thermoregulatory center, providing 40-65% VMS reduction without estrogenic effects. Gabapentin acts on voltage-gated calcium channels in the thermoregulatory center, reducing VMS by 45-50%. Fezolinetant (NK3 receptor antagonist) directly blocks neurokinin B signaling at the KNDy neuron, targeting the root mechanism of VMS. Tissue-selective estrogen complexes (conjugated estrogen/bazedoxifene) combine estrogenic VMS relief with bazedoxifene's selective estrogen receptor modulator activity that antagonizes estrogen on the endometrium and breast, eliminating the need for separate progestogen. The clinician selects pharmacotherapy based on VMS severity, patient risk profile (VTE history, breast cancer history, hepatic function, cardiovascular risk), drug interactions (CYP2D6 inhibition with tamoxifen), and shared decision-making.