ABSTRACT
Endocrine glands may secrete excessive or deficient amounts of hormone. Abnormalities of target glands may be primary or secondary to dysfunction of the controlling mechanism, usually located in the hypothalamus or anterior pituitary gland. The anterior and posterior lobes of the pituitary gland are developmentally and functionally distinct; both depend on hormones synthesized in the hypothalamus for normal function. Oxytocin is synthesized in the paraventricular nuclei of the hypothalamus. The hypothalamus synthesizes small molecules that are carried to the cells of the anterior pituitary lobe by the hypothalamic portal system. Extrahypothalamic neural stimuli modify, and at times over-ride, other control mechanisms. Physical or emotional stress and mental illness may give similar findings to, and even precipitate, endocrine disease. Growth hormone (GH) secretion from the anterior pituitary gland is mainly controlled by hypothalamic GH-releasing hormone. After synthesis by the hypothalamus, this is transported via the hypothalamic portal system to the somatotrophs of the anterior pituitary.
