Hypothalamus + Anterior Pituitary Hormones

Functional Relationship of the Hypothalamus and Anterior Pituitary

Hypothalamus produces Releasing and Inhibiting Hormones to control the anterior pituitary

Tropic Hormones (most of anterior pituitary hormones) control hormone secretion from other glands

(1) hypothalamic neurons secrete releasing and inhibiting hormones into the hypothalamic capillary bed

(2) hormones travel through portal veins in the infundibulum

(3) hypothalamic hormones exit the anterior capillary bed and bind to receptors on anterior pituitary cells

(4) hypothalamic hormones stimulate or inhibit secretion of hormones from the anterior pituitary cells

Negative Feedback Control of Anterior Pituitary Hormones

Hypothalamic hormones, anterior pituitary hormones, and hormones secreted by anterior pituitary's target tissues are maintained by negative feedback loops with multiple tiers, or levels, of control

First Tier controls the neuroendocrine cells of the hypothalamus

Second Tier controls the anterior pituitary cells

Third Tier controls the target tissue cells

Thyroid-Stimulating Hormone (TSH)

Also known as Thyrotropin

secreted by cells called Thyrotrophs

triggered by Thyrotropin-Releasing Hormone (TRH, first tier) from the hypothalamus

inhibited by Somatostatin (first tier) from the hypothalamus

stimulates development of the thyroid gland and its secretion of thyroid hormones

Adrenocorticotropic Hormone (ACTH)

Also known as Corticotropin

secreted by cells called Corticotrophs

triggered by Corticotropin-Releasing Hormone (CRH, first tier) from the hypothalamus

stimulates development of the adrenal glands and their steroid hormones

Prolactin

Produced by cells called Lactotrophs

primary target tissue is mammary gland cells

stimulates growth of the cells, initiation of milk production after childbirth, and maintenance of milk production for the duration of breast feeding

main stimulus is suckling of the nipple by an infant

inhibited by Prolactin-Inhibiting Factor from the hypothalamus (now known to be dopamine)

suckling decreases the release of dopamine

Luteinizing Hormone (LH)

Secreted by Gonadotrophs

one of two Gonadotropins

triggered by Gonadotropin-Releasing Hormone (GnRH) from the hypothalamus

stimulates testosterone production in testes in males and estrogens and progesterone production in ovaries in females and ovulation

Follicle-Stimulating Hormone (FSH)

the other gonadotropin

Stimulated by GnRH

stimulates cells in the testes to bind and concentrate testosterone in males

triggers production of estrogens and maturation of ovarian follicles in females