MODULE SUPPLEMENT: ENDOCRINE SYSTEM
Hypothalamic-Pituitary and Hypothalamic-Pituitary-Adrenal Axis
The hypothalamus has been considered a potential regulator of aging because of its central location and the widespread effects of its various neurohormones (Figure below). The hypothalamus receives input from, and sends signals to, the brain, and it produces neurohormones that stimulate or inhibit the release of other hormones from the anterior pituitary. In general, the system is under tight feedback control. We'll see that some of this control is less effective in older adults.
The major hypothalamic hormones of interest for this module include:
- Corticotropin releasing hormone (CRH)
- Somatostatin which is also called growth hormone inhibiting factor (GHIF)
- Growth hormone releasing factor (GHRF), and
- Thyrotropin releasing hormone (TRH).
CRH and TRH will be discussed in greater depth when the adrenal glands and the thyroid are discussed later. Thus the focus initially will be on GHRF and GHIF and their effects on growth hormone which is produced in the anterior pituitary.
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