Inhibin A is a protein hormone produced primarily by the ovaries in females and the testes in males. It plays a crucial role in regulating the reproductive system by inhibiting the secretion of follicle-stimulating hormone (FSH) from the pituitary gland. This helps control the growth and development of ovarian follicles in women and sperm production in men. Inhibin A levels can be measured through blood tests and are often used in fertility assessments and prenatal screening. Elevated levels of inhibin A during pregnancy can indicate certain conditions, such as Down syndrome, making it a valuable marker in maternal-fetal medicine.