Yes, progesterone increases body temperature. This reproductive hormone is the primary driver behind a subtle temperature shift in the female body. While internal temperature can fluctuate for many reasons, the change caused by progesterone is a predictable and natural part of the menstrual cycle.
The Thermogenic Effect of Progesterone
Progesterone has a thermogenic, or heat-producing, effect on the body. This process originates in the hypothalamus, a region in the brain that acts as the body’s thermostat. Progesterone influences this control center, causing it to reset the body’s thermal “set point” to a slightly higher level.
Once this set point is adjusted, the body generates and conserves more heat to meet the new baseline. This is driven by an increase in the basal metabolic rate, which can rise by 5-9% under the influence of progesterone. The result is a small but measurable increase in core body temperature, typically between 0.5 to 1.0°F (0.3 to 0.6°C). This elevation is not an indication of illness but a direct physiological response to the hormone.
The exact mechanism involves progesterone’s interaction with temperature-sensitive neurons in the preoptic area (POA) of the hypothalamus. It is thought that progesterone inhibits warm-sensitive neurons, which in turn reduces the body’s heat loss responses, such as vasodilation (the widening of blood vessels) near the skin. This action effectively traps more heat within the body, contributing to the sustained rise in core temperature.
Progesterone Fluctuation and Temperature Shifts in the Menstrual Cycle
The thermogenic effect of progesterone is most clearly observed across the menstrual cycle, which is divided into two main phases: the follicular and the luteal phase. Each phase is characterized by a different hormonal environment, leading to a distinct, biphasic temperature pattern. Understanding this rhythm is helpful for recognizing the different stages of your cycle.
The first half of the cycle is the follicular phase, which begins on the first day of your period. During this time, estrogen is the dominant hormone, and progesterone levels are very low. Consequently, your basal body temperature (BBT), which is your lowest resting temperature, remains in a lower range. This lower temperature phase lasts from menstruation until ovulation occurs.
Following ovulation, the cycle enters the luteal phase. The remnant of the ovarian follicle that released the egg transforms into a temporary gland called the corpus luteum. The primary function of the corpus luteum is to produce large amounts of progesterone to prepare the uterine lining for a potential pregnancy. It is this surge in progesterone that triggers the temperature increase, with the rise becoming evident about 24 hours after ovulation and stabilizing within 48 hours. This sustained higher temperature, lasting for the remainder of the cycle, is a reliable indicator that ovulation has successfully occurred.
Interpreting Your Basal Body Temperature
Tracking your basal body temperature can offer insights into your cycle’s progression. A chart that shows two distinct temperature levels—a lower one before ovulation and a higher one after—is known as biphasic. This pattern confirms that ovulation likely took place. The key is not a single day’s reading but the sustained shift over time.
The duration of the high-temperature phase is also meaningful. If you become pregnant, the corpus luteum continues to produce progesterone, and your temperature will remain elevated. A sustained high temperature for 18 or more days after ovulation is often an early sign of pregnancy.
If pregnancy does not occur, the corpus luteum begins to break down about 10 to 14 days after ovulation. This causes progesterone levels to fall sharply, which in turn signals your body to shed the uterine lining. This drop in progesterone also causes your basal body temperature to decline, typically a day or two before your period begins, starting the cycle anew. A chart that lacks a clear, sustained temperature shift may suggest an anovulatory cycle, where ovulation did not happen.
Factors That Can Influence Body Temperature Readings
While progesterone is the main driver of the cyclical temperature shift, other factors can influence your daily readings. It is important to be aware of these variables, as they can obscure the underlying pattern and make interpretation more difficult. Several other factors can influence readings:
- Illness or fever, which can mask the hormonal shift.
- Alcohol consumption, particularly the night before.
- Significant changes to your sleep schedule, such as getting too little or too much sleep.
- High levels of emotional or physical stress.
- Certain medications that interfere with thermoregulation.
- Travel across time zones that disrupts your internal clock.