What are Gonadotropin-Releasing Hormones?

Gonadotropin-releasing hormones are reproductive hormones that are produced in the hypothalamus of the brain. These hormones signal the pituitary gland to produce certain hormones involved in reproduction in both men and women. Reproductive hormone levels vary throughout life, remaining low in childhood, peaking when people are at reproductive age, and decreasing again as people grow older. In women, levels of reproductive hormones in the body vary in a cycle as women ovulate and menstruate.

This hormone is known as a neurohormone because it is synthesized in the neurons. The gonadotropin-releasing hormones are secreted by the same neurons that produce them in response to varying hormone levels that occur as part of a feedback cycle within the endocrine system. When gonadotropin-releasing hormones enter the pituitary gland, they signal the gland to start making follicle stimulating hormone (FSH) and luteinizing hormone (LH), and to release these hormones. The gonadotropins, as these hormones are known, travel to the testes and ovaries and play a role in reproduction.

In men, levels of gonadotropin-releasing hormones tend to remain fairly consistent. This is because men's reproductive systems do not follow a cycle like those of women. Levels of reproductive hormones gradually rise in puberty and stay consistent until men start to age. In women, the hormone levels fluctuate throughout the month. If the endocrine cycle that regulates the reproductive system becomes dysregulated, women may have difficulty becoming pregnant and they can also experience amenorrhea and other symptoms.

The gonadotropin-releasing hormones can also be introduced to the body in the form of synthetic hormones that are injected. They are sometimes used in women to treat conditions like endometriosis and thyroids, and as part of infertility treatment for women preparing for in vitro fertilization. Because hormone levels varies cyclically in women, the hormone injections must be timed to coincide with the existing hormone cycle. Before hormones are injected, blood testing is used to check hormone levels and confirm that the patient is a good candidate for hormone therapy.

When a patient presents to a doctor with infertility, hormone levels are one possible concern. Bloodwork can be used to evaluate a patient's hormone production and to look for obvious signs that the endocrine system is not operating normally. Other causes for infertility can also be explored, such as testing the sperm in men. Treatment for infertility can take time as doctors explore possible causes and present patients with treatment options.