Esophageal temperature threshold for sweating decreases before ovulation in premenopausal women

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Abstract
The purpose of this study was to test the hypothesis that regulated body temperature is decreased in the preovulatory phase in eumenorrheic women. Six women were studied in both the preovulatory phase (Preov-2; days 9–12), which was 1–2 days before predicted ovulation when 17β-estradiol (E2) was estimated to peak, and in the follicular phase (F; days 2–6). The subjects walked on a treadmill (∼225 W ⋅ m−2) in a warm chamber (ambient temperature = 30°C; dew-point temperature = 11.5°C) while heavily clothed. E2, esophageal temperature (Tes), local skin temperatures, and local sweating rate were measured. The estimate of when the E2 surge would occur was correct for four of six subjects. In these four subjects, E2 increased ( P ≤ 0.05) from 42.0 ± 24.5 pg/ml during F to 123.2 ± 31.3 pg/ml during Preov-2. Resting Tes was 37.02 ± 0.20°C during F and 36.76 ± 0.28°C during Preov-2 ( P ≤ 0.05). The Tes threshold for sweating was decreased ( P ≤ 0.05) from 36.88 ± 0.27°C during F to 36.64 ± 0.35°C during Preov-2. Both mean skin and mean body temperatures were decreased during rest in Preov-2 group. The hypothesis that regulated body temperature is decreased during the preovulatory phase is supported.