The pituitary gland has two sections: the posterior and the anterior pituitary. These sections have different origins and produce different hormones.
The posterior pituitary derives from nervous system tissue and produces neurohormones. The anterior pituitary derives from the epithelial tissue and produces hormones with endocrine functions.
With the onset of puberty, the hypothalamus increases the release of gonadotropin releasing hormone.
This causes the anterior pituitary gland to start producing follicle stimulating hormone (FSH) and lutenizing hormone (LH.)
These gonadotropins stimulate the production of the sex hormones estrogens and progestins. It is the interaction of the gonadotropins and the sex hormones that controls the reproductive cycle.