Hypothalamic–pituitary–gonadal axis in which the hypothalamus and pituitary direct neuroendocrine function. The hypothalamus is located in the brain and secretes GnRH. GnRH travels down the anterior portion of the pituitary via the hypophyseal portal system and binds to receptors on the secretory cells of the adenohypophysis. In response to GnRH stimulation these cells produce LH and FSH, which travel into the blood stream. These two hormones play an important role in communicating to the gonads. In females FSH and LH act primarily to activate the ovaries to produce estrogen and inhibin and to regulate the menstrual cycle and ovarian cycle. Estrogen forms
Anterior pituitary of three lobes: the anterior, intermediate, and posterior lobes. In many animals, these lobes are distinct. However, in humans, the intermediate lobe is but a few cell layers thick and indistinct; as a result, it is often considered as part of the anterior pituitary. In all animals, the fleshy, glandular anterior pituitary is distinct from the neural composition of the posterior pituitary. The anterior pituitary is composed of three regions: Nota bene: The term "Basophil" and "Acidophil" is used by some books, whereas others prefer to not use these terms. This is due to the possible confusion with white blood