Re: What causes bodyheat in male/female humans?.

Body temperature in homeotherms (mammals and birds) is controlled by a complex system of sensory nerves, hormones, and continuous feedback from the body called thermoregulation. The temperature of the body is kept high, because many of the enzymes required to keep the body running are temperature sensitive, that is they can only operate within a narrow range of temperatures. One plus to maintaining a high body temperature is that chemical reactions run faster, so homeotherms are more active. Another is that by being able to control their body temperatures, homeotherms can run fevers, a good mechanism for killing invading microbes.

Since body temperature is controlled by hormones, changing the levels of some hormones can alter the temperature of the body. For men, this isn't a concern since male hormone levels vary insignificantly. For women, hormone levels are not so invariant. During a normal menstrual cycle, a woman's hormones change dramatically, since several hormones are used to control progression through the cycle. Since some of these hormones' activities overlap the thermoregulatory system, they alter the woman's body temperature through the cycle.

Directly after menstruation, during the proliferative phase of the menstrual cycle, a woman's body temperature begins to drop below 98.6° F, perhaps as low as to 98.0° F (or lower in some women). Sometimes at ovulation there is a further drop in the woman's body temperature. A possible reason for this low body temperature is to prolong the life of and aid in the mobility of sperm, increasing their chances at fertilizing the egg being released. After ovulation, during the secretory phase, the body temperature rises to 98.6° F or higher, until menstruation when it returns to "normal" again.