The primary function of the glycoprotein hormone FSH in the female is the regulation of follicle growth. FSH is produced and secreted by the anterior lobe of the pituitary, a gland at the base of the brain. Its target is the FSH receptor at the surface of the granulosa cells that surround the oocyte. FSH acts synergistically with oestrogens and LH to stimulate proliferation of these granulosa cells, which leads to follicular growth. This process explains why deficient endogenous production of FSH may cause infertility.