- Identify the 3 families of anterior pituitary hormones and their main structural differences.
- Understand the mechanisms that regulate anterior pituitary hormone production and describe the actions of tropic hormones on target organs.
- Diagram the short-loop and long-loop negative feedback control of anterior pituitary hormone secretion.
- Predict the changes in secretory rates of hypothalamic anterior pituitary and target gland hormones caused by oversecretion or undersecretion of any of these hormones or receptor deficit for any of these hormones.
- Explain the importance of pulsatile and diurnal hormone secretion.
The anterior pituitary, or adenohypophysis, plays a central role in the regulation of endocrine function through the production and release of tropic hormones (Figure 3–1). The function of the anterior pituitary, and thereby the production of tropic hormones, is under hypothalamic regulation by the hypophysiotropic neuropeptides released in the median eminence, as discussed in Chapter 2 and summarized in Table 3–1. The tropic hormones produced by the anterior pituitary are released into the systemic circulation, from where they reach their target organs to produce a physiologic response, most frequently involving the release of a target organ hormone (see Figure 3–1). The hormones produced by the target organs affect anterior pituitary function as well as the release of hypophysiotropic neuropeptides, maintaining an integrated feedback control system of endocrine function (see Chapter 1, Figure 1–12).
Anterior pituitary hormones, target organs, and physiologic effects. Thyroid-stimulating hormone (TSH) stimulates the thyroid gland to produce and release thyroid hormones that regulate growth, differentiation, and energy balance. Luteinizing hormone (LH) and follicle-stimulating hormone (FSH) stimulate gonadal production of sex steroids, which mediate reproductive function and behavior. Adrenocorticotropic hormone (ACTH) stimulates the adrenal glands to produce steroid hormones, which regulate water and sodium balance, inflammation, and metabolism. Prolactin (Prl) stimulates breast development and milk production. Growth hormone (GH) exerts direct effects on tissue growth and differentiation and indirect effects through the stimulation of insulin-like growth factor 1 production, which mediates some of the growth and differentiation effects of GH.
Table 3–1. Anterior Pituitary Cell Type, Regulatory Hypothalamic Factor, and Hormone Product |Favorite Table|Download (.pdf)
Table 3–1. Anterior Pituitary Cell Type, Regulatory Hypothalamic Factor, and Hormone Product
|Anterior pituitary cells||Hypothalamic factor||Pituitary hormone produced|
|Corticotrophs||CRH||POMC: ACTH, β-LPH, α-MSH, β-endorphin|
|Gonadotrophs||GnRH||LH and FSH|
The pituitary, or hypophysis, consists of an anterior and a posterior lobe that differ from one another in their embryologic origin, mode of development, and structure. The anterior lobe, also known as the adenohypophysis, is the larger ...