Activin and inhibin

Activin and Inhibin

Diagram illustrating the structure of activin and inhibin.

Activin and inhibin are two closely related protein complexes that play crucial roles in the regulation of various physiological processes, including the reproductive system, cell growth, and immune response. Both activin and inhibin are members of the transforming growth factor beta (TGF-_) superfamily, which is involved in the regulation of cell proliferation, differentiation, and apoptosis.

Structure

Activin and inhibin are dimeric proteins, meaning they are composed of two subunits. These subunits are linked by disulfide bonds.

Activin

Activin is formed by the dimerization of two beta subunits, which can be either _A or _B. The most common forms of activin are activin A (_A-_A), activin B (_B-_B), and activin AB (_A-_B).

Inhibin

Inhibin is composed of one alpha (_) subunit and one beta (_) subunit. The two main forms of inhibin are inhibin A (_-_A) and inhibin B (_-_B).

Function

Activin

Activin primarily functions to stimulate the secretion of follicle-stimulating hormone (FSH) from the anterior pituitary gland. It also plays a role in the regulation of the menstrual cycle, wound healing, and the immune system.

Inhibin

Inhibin acts as an antagonist to activin by inhibiting the secretion of FSH. It is involved in the negative feedback regulation of the hypothalamic-pituitary-gonadal axis, helping to control the production of gametes and sex hormones.

Biological Significance

Activin and inhibin are critical in maintaining the balance of reproductive hormones. They ensure the proper functioning of the ovaries and testes, influencing spermatogenesis and oogenesis.

Clinical Implications

Abnormal levels of activin and inhibin can be indicative of various medical conditions. Elevated levels of inhibin, for example, can be associated with certain types of ovarian cancer. Conversely, altered activin levels may be involved in infertility and endometriosis.

Related Pages

• Transforming growth factor beta
• Follicle-stimulating hormone
• Reproductive system
• Hypothalamic-pituitary-gonadal axis