Esophageal temperature threshold for sweating decreases before ovulation in premenopausal women

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 17beta-estradiol (E2) was estimated to peak, and in the follicular phase (F; days 2-6). The subjects walked on a treadmill ( approximately 225 W x m-2) in a warm chamber (ambient temperature = 30 degreesC; dew-point temperature = 11.5 degreesC) 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 degreesC during F and 36.76 +/- 0.28 degreesC during Preov-2 (P </= 0.05). The Tes threshold for sweating was decreased (P </= 0.05) from 36.88 +/- 0.27 degreesC during F to 36. 64 +/- 0.35 degreesC 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.

Hormonal Contraception, Body Water Balance and Thermoregulation

“…Endogenous progesterone and estrogen often have opposing effects on regulatory systems, and the presence of high levels of progesterones in the blood down-regulate estrogen receptors. This is consistent with the recent finding that the fall in the temperature thresholds for sweating onset of cutaneous vasodilation was related not only to the estrogen peak prior to ovulation, but also related to the ratio of E 2 to P 4 levels in the blood (94). The varying ratios of these hormones between the mid-luteal and OC E+P may explain the differing temperature responses in the present investigation.…”

“…Plasma arginine vasopressin concentration is elevated in the presence of a high concentration of plasma estrogens in humans (32,33). Plasma concentration of arginine vasopressin is increased during the mid-follicular phase of the menstrual cycle in young women (32) and following the administration of exogenous estrogen in post-menopausal women (33), although these increases are inconsistent when progesterone is increased along with estrogen (32,92).…”

“…Plasma concentration of arginine vasopressin is increased during the mid-follicular phase of the menstrual cycle in young women (32) and following the administration of exogenous estrogen in post-menopausal women (33), although these increases are inconsistent when progesterone is increased along with estrogen (32,92). Late pregnancy, a state characterized by elevated sex hormone levels, is associated with an altered threshold for arginine vasopressin release due to normal AVP levels combined with reduced P 0sm .…”

“…Haslag and Hertzman (44) demonstrated that the onset of thermoregulatory sweating during whole body heating occurred at a lower core temperature in women during their follicular phase. Stephenson and Kolka reported lower core temperature thresholds of both sweating (53,94,95) and cutaneous vasodilation in a hot environment (94, 95) during the follicular phase. No studies have assessed directly the effect of oral contraceptives on thermoregulatory responses during exercise in the heat, but the thresholds for the onset of sweating and vasodilation were reduced by 0.47°C and 0.48°C, respectively following 2 weeks of estrogen replacement therapy in post-menopausal women (106), and was reduced during long term estrogen therapy (13).…”

Luteal phase of the menstrual cycle increases sweating rate during exercise

“…Evidence about the possible effect of the menstrual cycle on thermoregulation during exercise is scarce and contradictory (6)(7)(8)(9)(10)(11), although the importance of controlling for the menstrual cycle in thermoregulation studies involving fertile women has been repeatedly emphasized (12)(13)(14).…”