Follicle Stimulating Hormone (FSH) is a vital reproductive hormone that plays a central role in the regulation of the human reproductive system.
It is a gonadotropin, meaning it stimulates the activity of the gonads—ovaries in females and testes in males. FSH is produced and secreted by the anterior pituitary gland, under the control of the hypothalamus, which releases Gonadotropin-Releasing Hormone (GnRH) to stimulate its production.
In females, FSH is primarily responsible for the growth and maturation of ovarian follicles, which are essential for ovulation and fertility. In males, it supports the function of Sertoli cells in the testes, which are critical for the production and development of sperm.
Follicle Stimulating Hormone (FSH) – Normal Range
The normal range of Follicle Stimulating Hormone (FSH) varies depending on age, gender, and the stage of the reproductive cycle. FSH levels are usually measured through a blood test and are reported in international units per liter (IU/L).
Normal FSH Levels
In Women
| Stage | Normal Range (IU/L) |
|---|---|
| Follicular Phase | 3.5 – 12.5 IU/L |
| Ovulation (Mid-cycle peak) | 4.7 – 21.5 IU/L |
| Luteal Phase | 1.5 – 9.0 IU/L |
| Postmenopausal | 25.8 – 134.8 IU/L |
In Men
| Category | Normal Range (IU/L) |
|---|---|
| Adult males | 1.5 – 12.4 IU/L |
In Children
| Category | Normal Range (IU/L) |
|---|---|
| Prepubescent (both sexes) | 0.3 – 3.0 IU/L |
Note:
- These values may slightly differ between laboratories.
- FSH levels are often interpreted along with LH (Luteinizing Hormone) and sex hormone levels (like estrogen or testosterone) to assess reproductive health.
Functions of Follicle Stimulating Hormone (FSH) in Females
Follicle Stimulating Hormone (FSH) plays a central role in the female reproductive system, especially in regulating the menstrual cycle, egg development, and hormonal balance.
It is produced by the anterior pituitary gland and works in coordination with Luteinizing Hormone (LH) and estrogen to maintain fertility and prepare the body for potential pregnancy.
1. Stimulation of Ovarian Follicles
FSH stimulates the growth and maturation of ovarian follicles during the first half of the menstrual cycle (follicular phase). Each follicle contains an immature egg (oocyte), and FSH encourages one of them to develop into a dominant follicle ready for ovulation.
2. Estrogen Production
As the follicles grow, FSH stimulates the granulosa cells inside them to produce estrogen. Rising estrogen levels prepare the uterine lining (endometrium) for the possible implantation of a fertilized egg.
3. Regulation of the Menstrual Cycle
FSH helps initiate the follicular phase of the menstrual cycle. The hormone works with LH to control the timing of ovulation, and estrogen produced in response to FSH provides feedback to the brain to regulate further hormone release.
4. Selection of Dominant Follicle
Among several developing follicles, FSH helps in the selection of one dominant follicle, which will continue to grow and eventually release an egg during ovulation.
Functions of Follicle Stimulating Hormone (FSH) in Males
In males, Follicle Stimulating Hormone (FSH) is a vital hormone for maintaining proper reproductive function.
It is secreted by the anterior pituitary gland and acts primarily on the testes to support sperm production and testicular development.
1. Stimulation of Spermatogenesis
FSH stimulates the Sertoli cells located within the seminiferous tubules of the testes. These cells provide physical and nutritional support necessary for the production and maturation of sperm cells (a process called spermatogenesis).
2. Maintenance of Sertoli Cell Function
Sertoli cells rely on FSH to function properly. FSH promotes the secretion of various proteins and growth factors by these cells, which are essential for nurturing developing sperm.
3. Support for Testicular Growth
During puberty, FSH contributes to the growth and development of the testes, preparing them for full reproductive function.
4. Regulation of Hormonal Feedback
FSH levels are controlled by a negative feedback mechanism involving inhibin, a hormone secreted by Sertoli cells. When sperm production is sufficient, inhibin levels rise and signal the pituitary gland to reduce FSH secretion.