Endocrine Drugs and Medications Q 14
Which of the following is a contraindication to the administration of growth hormone?
A. The height of the child is under 4 feet
B. The child's age is between 5 and 6
C. The epiphyseal shaft is open
D. The epiphyseal shaft is closed
Correct Answer: D. The epiphyseal shaft is closed
A closed epiphyseal shaft is a contraindication for administration of growth hormone. Human growth hormone is produced via the anterior pituitary of the brain in the acidophilic, somatotrophic cells. Its production is tightly regulated through several complex feedback mechanisms in response to stress, exercise, nutrition, sleep, and growth hormone itself. The primary regulation factors are growth hormone-releasing hormone (GHRH) produced in the hypothalamus, somatostatin, produced in various tissues throughout the body, and ghrelin, which is produced in the gastrointestinal tract. There are no exact height or age requirements for the administration of growth hormone.
Option A: GHRH functions to promote HGH production and release. Somatostatin inhibits the release of GHRH as well as the HGH release response to GHRH stimulus and increases in hypoglycemia. Ghrelin is a hormone produced by the stomach as part of the hunger response. Functionally, the ghrelin response is protective against hypoglycemia. When elevated, ghrelin binds to somatotrophs to stimulate HGH secretion.
Option B: Insulin-like growth factor-1 also acts to inhibit HGH by both directly inhibiting somatotrophic HGH release and indirectly through synergistically increasing the release of somatostatin. Additionally, HGH will negatively feedback into the hypothalamus, thus decreasing GHRH production. The net effect of this regulatory mechanism produces a pulsatile release of HGH into circulation that varies hourly.
Option C: In general, HGH levels will be increased in childhood, spike to their highest levels during puberty, and subsequently decrease with increased age. HGH has two mechanisms of effect: direct action and indirect action. The direct effects of HGH on the body are through its action on binding to target cells to stimulate a response. The indirect effects occur primarily by the action of insulin-like growth factor-1, which hepatocytes primarily secrete in response to elevated HGH binding to surface receptors.