Pituitary and Pineal Glands

Pituitary Gland is split into two parts:

• Adenohypophysis, which is further broken into pars distalis (anterior lobe), pars tuberalis, and pas intermedia. The anterior lobe is made of the following five cell types:
• Somatotropes (GH cells) produce somatotropin or growth hormone. It functions by causing growth of long bones via somatomedins (insulin like growth factor 1), and is synthetized in the liver. It is stimulated by growth hormone releasing hormone (GHRH) and inhibited by somatostatin.
• Lactotropes/Mammotropes (PRL cells) produce prolactin. It functions by promoting milk secretion, and increasing mammary gland in size during pregnancy and lactation. It is (potentially) stimulated by PRH and inhibited by PIH (dopamine - catecholamine).
• Thyrotropes (TSH cells) produce thyrotropin (TSH). It functions by stimulating thyroid hormone synthesis, storage, and liberation. It is stimulated by TRH (thyrotropin-releasing hormone).
• Gonadotropes (FSH and LH cells) produce FSH (follicle stimulating hormone) and LH (luteinizing hormone). FSH functions by promoting ovarian follicle development and estrogen secretion in women and stimulates spermatogenesis in men. LH functions by promoting ovarian follicle maturation and progesterone secretion in women and Leydig cell stimulation and androgen secretion in men. They are stimulated by GnRH (gonadotropin release).
• Corticotropes (ACTH cells) produce corticotropin (ACTH). It functions by stimulating secretion of adrenal cortex hormones. It is stimulated by CRH (corticotropin-releasing hormone).
• Cells that produce growth hormone and prolactin are called acidophils, cells that produce FSH, LH, TSH, and ACTH are basophils, and chromophobes have depleted their hormone content.
• Neurohypophysis, which is further broken into the pars nervosa (neural lobe) and the infundibulum (made of the infundibular process and median eminence). Axons in the neurohypophysis are derived from the supraoptic nuclei and the paraventricular nuclei. The pituicytes are astrocyte-like glial cells.

Pineal gland is made of two cell types, the pinealocytes and glial-like interstitial cells (astrocytes). The pineal gland secretes the highest level of melatonin during night to induce sleepiness.