The Impact of Melatonin on Hormone Production and Development

Introduction

People with insomnia have trouble sleeping at nighttime. This is where melatonin comes into play. However, information about the long-term safety of melatonin is lacking. Light during the night blocks or decreases melatonin production, signaling the body to be awake. Melatonin is mainly triggered by darkness that signals the body to sleep. People mostly use melatonin to improve sleep in situations like jet lag. It is used in hypertensive patients (high blood pressure). Hypertensive patients take beta-blockers to reduce their pressure. Beta-blockers have the ability to cause insomnia (not being able to sleep properly during the night). It is also called the hormone of darkness.

What Is Melatonin?

Melatonin is a natural hormone produced by the pineal gland in the brain. It plays a crucial role in the sleep-wake cycle of the body. The pineal gland is a small gland in the brain. Circadian rhythms mean the mental and physical behavior of the person. It is also called the 'sleep hormone' released in the presence of darkness. It helps regulate the circadian rhythm along with sleep. Melatonin will be blocked if there is light in the night. Melatonin supplements help in conditions such as delayed sleep-wake cycle, jet lag, sleep disorders, and anxiety after and before surgery.

What Are the Functions of Melatonin?

The functions of melatonin are-

• It has a significant role in circadian rhythms (the internal clock in the brain that regulates alertness and sleepiness by responding to light).

• It is considered the body’s natural pacemaker because it works by signaling the time and day of the year that regulates the body’s internal clock.

• It plays an important role in regulating the female menstruation cycle and has an influential role in regulating sleep cycles.

• It has anti-aging properties and has the ability to modulate the immune system. It is also effective in oxidative stress. It achieves this by removing the free radicals by activating the antioxidant enzymes.

• Melatonin has important functions in fertilization and oocyte maturation. It binds to its receptors in the pituitary gland and regulates the release of female reproductive hormones.

How Does Melatonin Influence Hormonal Development?

• Melatonin does not directly affect hormone production but indirectly influences other hormones in the body. Melatonin affects hormone production by regulating the hypothalamus-pituitary-gonadal (HPG) axis activity. Melatonin inhibits the release of gonadotropin-releasing hormone (GnRH) from the hypothalamus, which in turn reduces the secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) from the pituitary gland. This leads to decreased sex hormone production.

• Melatonin also influences the production of insulin, cortisol, and growth hormone. Melatonin increases the secretion of growth hormone, thus regulating glucose metabolism. The hypothalamus in the brain is the region that controls hormone release from the pituitary gland. Gonadotropin-releasing hormone from the hypothalamus stimulates the secretion of luteinizing hormone and follicle-stimulating hormone from the hypothalamus. Melatonin inhibits the release of gonadotropin-releasing hormones from the hypothalamus, thus leading to decreased secretion of follicle-stimulating hormone (FSH) and luteinizing hormone (LH).

• FSH and LH are important for reproduction, involving testosterone production in men and ovulation in women.

• Studies show that melatonin inhibits luteinizing hormone (LH) release from the pituitary gland. Luteinizing hormone is responsible for testosterone production in the testes. The inhibition of LH by melatonin can lead to a decrease in testosterone levels in men.

• Studies show that melatonin reduces the secretion of cortisol. High melatonin levels signal the hypothalamus to decrease the release of corticotropin-releasing hormone. This, in turn, decreases the adrenocorticotropic hormone (ACTH) release from the pituitary gland. ACTH is the hormone involved in the production of cortisol from the adrenal gland. At low levels of melatonin, there is a high level of cortisol.

• The estrogen is very low in women after menopause. Insomnia (inability to sleep at night) is a common problem faced by menopausal women. The symptoms of postmenopausal women are vaginal dryness, sexual dysfunction, and mood disturbances, mainly because of low estrogen. Restlessness, mood disturbances, and other symptoms are mainly because of low estrogen.

• Estrogen lowers the body temperature and makes the body conducive to restful sleep. Melatonin is a hormone affected by light. Estrogen produces neurotransmitters that affect the sleep-wake cycle, keep the body temperature low at night, and are more conducive to restful sleep. The cause of appetite and increased weight is due to estrogen deficiency in postmenopausal women. There is a drop in melatonin in menopausal women that leads to poor concentration, fatigue, and decreased sleep.

• Some studies suggest that melatonin has a direct effect on estrogen receptors. Melatonin binds to estrogen receptors and modulates their activity. Some studies suggest that melatonin may have anti-estrogenic effects by inhibiting the aromatase enzyme. Aromatase enzymes are responsible for converting androgens into estrogens.

• Some studies show no difference in the hormonal synthesis of follicle-stimulating hormone (FSH), luteinizing hormone (LH), and testosterone after administration of melatonin.

• Recent studies do not confirm the role of melatonin in modulating testosterone (male reproductive hormone).

• The melatonin-treated female rats showed decreased luteinizing hormone and estradiol levels and a significant increase in progesterone levels.

• Hypomelatonimenia is a state where the melatonin levels are lower than normal level. The symptoms of improper melatonin production include irregular sleep-wake rhythm and advanced sleep phase disorder.

• The men who are under testosterone treatment have decreased melatonin levels.

• The nocturnal secretion of melatonin is increased in women using oral contraception.

• Estrogens are administered to postmenopausal women because postmenopausal women have a low secretion of melatonin at night. Estrogen also affects the melatonin's nocturnal peak, secretion duration, and circulation levels.

Conclusion

Melatonin levels are high during the night and low during the day. They are very important for sleep in a person; hence, they are called sleep hormones. Melatonin is triggered by darkness and blocked by light. Melation helps to stimulate sleep in high blood pressure patients and reduces stress. People use melatonin to improve sleep in situations with jet lag conditions. It is used in hypertensive patients (high blood pressure) to stimulate sleep and reduce stress. Reproductive hormones and melatonin have a circadian rhythm relationship. Reproductive hormones influence circadian concentration and melatonin production. The melatonin variations during the day also influence reproductive hormones.