Follicle-Stimulating Hormone, abbreviated as FSH, is a key gonadotropic hormone, along with another biochemical substance known as luteinising hormone (LH). Gonadotropic hormones refer to hormones that activate the gonads i.e. sex glands – ovaries in women and testes in men, to perform their primary reproductive, sexual and accessory functions in the body. FSH is synthesised and subsequently released into the bloodstream by the pituitary gland, upon the actions of gonadotrophin-releasing hormone situated in the hypothalamus in the brain. Once in circulation, FSH attaches to receptors in the ovaries and testes and exerts its functional effects on the reproductive organs, such as sexual development, puberty and maturation.
Follicle-Stimulating Hormone And Its Structure:
The key role of the pituitary gland in the regulation of reproductive and sexual characteristics in men and women, by the synthesis of two hormones, was established by the renowned German scientist Zondek. In 1929 – 1930, through extensive research, he proved that follicle-stimulating hormone and luteinising hormone influenced the cellular and tissue activities of the endometrium and vaginal epithelium in women.
However, the follicle-stimulating hormone was first successfully isolated only in the following year in 1931, by three reputed American researchers – Fevold, Hisaw and Leodard. They separated the two protein hormones – FSH and LH – from hog anterior lobes and discovered that FSH kindled ovarian follicular development and sexual maturity in immature rats, while LH stimulated the activated follicles by FSH to luteinize i.e. develop into the corpus luteum, for further reproductive and sexual functions.
Follicle-Stimulating Hormone is a protein hormone that presents as a glycoprotein heterodimer. It has two polypeptide units – alpha with 96 amino acids and beta with 111 amino acids, with the beta unit conferring it with the potential to influence the reproductive organs – the ovaries and testes. The sugar fragment of the FSH is bound to the amino acid asparagine and the molecular weight of the follicle-stimulating hormone is 35.5 kDa (kilo Daltons, with dalton being a central unit of atomic mass).
Functions Of Follicle-Stimulating Hormone:
The follicle-stimulating hormone carries out various vital functions in the body, including:
Regulating the menstrual cycle in women, by enhancing the formation and development of eggs in the ovaries. FSH levels fluctuate constantly in women, with the highest volumes occurring prior to an egg being released by the ovary – a process termed ovulation.
Acting on the testes in men to modify the synthesis of sperm, with FSH levels not altering to a large extent
Boosting sexual development in girls and boys during puberty, by controlling the ovaries in girls to secrete estrogen and signalling the testes in boys to produce testosterone, both of which are key reproductive hormones
Adverse Effects Of Hormonal Imbalance In Follicle-Stimulating Hormone:
Lesser than normal levels of FSH hamper the gonadal function in men and women – a condition known as hypogonadism. This, in turn, triggers numerous health issues such as:
- Polycystic Ovarian Syndrome (PCOS), with the growth of cystic lumps in the ovaries in women
- Obesity in women
- Infertility in women
- Hirsutism, an ailment wherein there is excess facial and body hair in women
- Low sperm count in men
- Kallmann Syndrome, a genetic disorder that impedes the onset of full completion of puberty
FSH levels are naturally high in women undergoing menopause, with the hormone instigating menopausal complications of osteoporosis, heart disease. However, when FSH levels are high in the reproductive years between 15 – 49 years, it results in several health anomalies, such as:
- Premature menopause in women
- Poor ovarian reserve in women
- Genetic disorders of Turner syndrome in women and Klinefelter syndrome in men