Hypothalamus: Regulatory Hormones

Hormones from hypothalamus are called regulatory hormones because they are molecules secreted into the blood to regulate the secretion of the anterior pituitary hormones. There are two groups of regulatory hormones. Group one is called releasing hormones which stimulate the production and secretion of the anterior pituitary hormones. Group two is called inhibiting hormones which deter the production and secretion of the anterior pituitary hormones. In this writing assignment we are focusing on releasing hormones. The hypothalamus consists of interconnecting neurons. Neurotransmitters, made up by a transmission of an electrical impulse and the secretion of a chemical substance, diffuses across the synapse of a presynaptic membrane on one neuron to the postsynaptic membrane of another neuron (Utiger, 2014). When a specific

hormone is produced within the hypothalamus, they are released into the primary plexus and transported by the hypophyseal portal vein to reach the secondary plexus located within the anterior pituitary.

There are five hypothalamic hormones that stimulate the anterior pituitary and are called tropic hormones. The first is called Thyrotropin-releasing Hormone (TRH) which increases the secretion of thyroid-stimulating hormone (TSH) and stimulates the release of thyroid hormone from the thyroid gland. The second is Prolactin-releasing hormone (PRH) which increases the secretion of prolactin (PRL) and primarily regulates breast milk in women. Gonadotropin-releasing hormone (GnRH) is the third and it increases the secretion of the follicle-stimulating hormone (FSH) and luteinizing hormone (LH) which regulates the production and maturation of sperm and oocytes as well as hormonal synthesis by the gonads. The fourth hormone is called Corticotropin-releasing hormone (CRH) which increases the secretion of adrenocorticotropic hormone (ACTH) that stimulates the adrenal cortex to produce and secrete corticosteroid hormones. An example of a corticosteroid hormone is cortisol. Lastly, the fifth hormone is the Growth hormone-releasing hormone (GHRH) which increases the secretion of growth hormone (GH) that stimulates cell growth throughout the

entire body. Primary examples of where GH stimulates growth is in cartilage, bone, muscle tissue, and adipose connective tissue.

Graves’ disease is a condition of hyperthyroidism. There are several symptoms of Graves’ disease. The more common ones are ingestion of T4, excessive stimulation of the thyroid by the pituitary gland, loss of feedback control by the thyroid, and peculiar change in the eyes known as exophthalmos. Exophthalmos means protruding or bulging eyeballs. The simple answer to how Graves’ disease relates to this topic is homeostasis. In the case of the thyroid hormone the hypothalamus is stimulated by something (decreased thyroid hormone, cold weather, pregnancy, high altitude, and hypoglycemia). Our receptors respond and signal the control center to release thyrotropin-releasing hormone into the hypothalamo-hypophyseal portal system. In response, the anterior pituitary releases thyroid-stimulating hormone, which stimulates the thyroid gland to release thyroid hormone into the blood. Thyroid hormone release is very tightly controlled in a healthy state, but if the amount differs even the slightest bit, it will throw off the thyroid hormone balance in the body. If the thyroid hormone balance is off in the body, then the results can lead to hyperthyroidism. And a condition of hyperthyroidism is Graves’ disease.