Estrogen and Thermoregulation - An Overview

Introduction

Body temperature regulation system under the direction of estrogen. Hot flushes and night sweats are symptoms of low estrogen levels, causing the body temperature to rise. Couples may be able to anticipate ovulation by observing temperature fluctuations during the menstrual cycle. Impact of estrogens on central autonomic nuclei responsible for sweating and cutaneous blood flow regulation. Through their direct impact on peripheral blood arteries, estrogen promotes vasodilation.

What Is Estrogen?

It is a hormone associated with the female sex and responsible for developing female sexual characteristics. Three major endogenous estrogens that have estrogenic hormonal activity are

• Estrogen.

• Estradiol.

• Estriol.

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Among all, estradiol is the most potent; the effects of estrogens on the body are -

• It causes breast development during puberty in females.

• It is also responsible for the development of mammary ducts during pregnancy.

• It thickens the endometrial lining in preparation for pregnancy.

• Vagina supports the proliferation of mucosal epithelial cells of the vagina and the vulva.

• During puberty, estrogen helps develop long bones and the fusion of the epiphyseal growth plates.

• Estrogen protects bones by inactivating osteoclast activity, preventing osteoporosis (bones become weak and brittle) in both.

• In the cardiovascular system, estrogen affects plasma lipids by increasing high-density lipoproteins and triglyceride levels while decreasing low-density lipoproteins and total plasma cholesterol and reducing the risk of coronary artery disease.

What Is Thermoregulation?

Thermoregulation is a homeostatic process that keeps body temperature within acceptable limits; normal body temperature is 98.6 degrees Fahrenheit or about 37 degrees Celsius. If thermoregulation is considered, then the thermal gradient should also be considered. It is the difference between ambient temperature and body temperature. The ambient temperature could be higher or lower than the body temperature depending on the weather, and that also tells us the direction of the gradient, so heat transfer will always be heat flow from high to low temperature; therefore, if the body temperature is lower than the temperature outside then the body will gain heat from the environment and conversely, if the body temperature is higher than the temperature outside the body will lose heat to the environment. This way, the body regulates the body temperature, so there are a couple of important mechanisms of thermogenesis or heat production, including work-induced, diet-induced, and shivering.

Releasing things like epinephrine and glucagon thyroid hormone can all increase metabolic activity and heat. Then the principles of thermal lysis or heat loss include conduction which is the direct transfer of heat through physical contact. It travels through high to low convection, basically the loss of heat to the air that overlies the heat source, and typically this occurs by utilizing air currents that pass over the body.

What Physiology Governs Body Temperature Regulation?

The preoptic area of the anterior hypothalamus (PO/AH), the leading central nervous system site for control and coordination of efferent thermoregulatory responses, is where thermoregulation is performed by the integration of central and peripheral thermal information. In contrast, during drops in body temperature (hypothermia), both heat generation (via shivering) and heat conservation (via cutaneous vasoconstriction) help to maintain core temperature. Human heat dissipation during rises in body temperature (hyperthermia) depends on cutaneous vasodilation and sweating. An overview of these human thermoregulatory processes will be given in the sections that follow as a foundation for discussing the effects of sex hormones on these reactions.

What Is the Thermogenic Effect of Estrogen?

Several metabolic, circulatory, and neuroendocrine alterations are linked to declining and fluctuating estrogen levels throughout menopause (at the age of 45 or above 45 when menstruation is in the declining stage); estrogen is one of the sex hormones, and it regulates menstruation in females. The vasomotor symptoms, which include hot flashes and nocturnal sweats, are the typical side effects of perimenopause. Hormone therapy is frequently used to treat vasomotor symptoms. The neuronal and molecular estrogen targets many brain areas that regulate various aspects of temperature regulation. These findings imply that estrogens may influence how many specialized brain circuits coordinate the range of changes that occur after menopause.

In the United States, 75 percent to 80 percent of menopausal women report experiencing hot flashes, which last an average of 7.4 years and are characterized by episodic and temporary increases in skin vasodilation, sweating, and shaking. With estrogen therapy, hot flashes connected to times of estrogen withdrawal from menopause can be effectively avoided. Although hormone therapy is an effective treatment for hot flashes, its hazards, such as the chance of developing reproductive malignancies, have limited its usage. Less effective lifestyle changes and medication therapies are available as alternatives.

How Does the Estrogen Receptor (Alpha and Beta) Affect Thermoregulation?

Estrogens are sex hormones well known for their role in female reproduction. Estrogen, estradiol, and estriol are the three main endogenous estrogens, with 17-estradiol (E2) being the main circulating estrogen in a female's menstrual cycle. Although local estrogen production occurs in many non-reproductive organs, including the brain, most E2 is produced in the ovaries. Site-specific or cell-type-specific estrogen metabolism and function are made possible by the local production of estrogens, independent of systemic circulation levels. Estrogen receptors alpha and beta and the G protein-coupled estrogen receptor (GPER1) play a significant role in the biological effects of estrogens. Nuclear receptor impacts on nucleus-initiated transcription can change gene expression due to estrogen receptor activation.

Estrogens control fluid vaporization and cutaneous vasoconstriction (CVC), which impact heat dissipation. The exact mechanisms underpinning how estrogens affect heat dissipation are still largely unclear, but the data to date points to a critical function for neurons in the median preoptic nucleus (MPO). Neurons process skin thermosensory inputs in the MPO, sending direct and indirect projections to sympathetic premotor neurons in the RPA, which control sympathetic vasoconstrictor nerves. Numerous studies have revealed that the hypothalamus contains several estrogen-sensitive areas, including the ARC, MPO, and MPA, and an estrogen-sensitive circuit (ARC-MnPO-MPA-RPA) that regulates heat dissipation at the skin.

Conclusion

Several estrogen-sensitive regions have been identified to mediate the effects of estrogen on body temperature. However, evidence suggests that these regions act in concert, antagonistically, or simultaneously to influence whole-body thermoregulation. While estrogens modulate heat generation and dissipation to impact body temperature, many of these actions are mediated by various estrogen-sensitive areas, either separately or simultaneously.

The thought of hot flashes and other premenopausal symptoms may be foreign to women who experience them. They may mistakenly believe that cardiac disease is to blame, leading to ineffective treatment. This issue can be solved with education and lifestyle changes. The line of treatment is called hormone therapy. Still, unfortunately, it has serious adverse effects like malignancy, so lifestyle modification which includes physical activity, weight loss, a nutritious diet, and giving up alcohol and smoking, is a preferable option. After all of this, it will considerably help naturally.