[47.2] A 7-year-old child who was very small for his age began receiving
treatment with growth hormone. Which one of the following metabolic
alterations is most likely to be observed after beginning this treatment?
A. Inhibition of cartilage formation
B. Inhibition of gluconeogenesis
C. Inhibition of triglyceride breakdown and oxidation in adipocytes
D. Stimulation of IGF-1 secretion
E. Stimulation of protein breakdown
[47.3] The following polypeptide hormones each interact with receptors in
the plasma membrane of their target cells. Which one triggers a sig-
naling pathway that is directly stimulated by treatment of the cell with
an inhibitor of cyclic AMP phosphodiesterase?
B. Epidermal growth factor
C. Growth hormone
E. Nerve growth factor
A nsw ers
B. The symptoms are consistent with acromegaly, or GH overpro-
duction, in the adult. This condition usually is caused by a pituitary
tumor. In the female, breast milk secretion is sometimes observed,
either as a result of GH overproduction or an accompanying overpro-
duction of prolactin. Growth hormone opposes insulin action result-
ing in decreased glucose utilization and symptoms of diabetes
mellitus. Growth hormone also increases IGF-1 production by the
liver, leading to stimulation of cartilage synthesis and muscle mass.
Excessive bone and tissue growth lead to the characteristic coarse
facial features, enlarged tongue and heart, bone thickening, and other
characteristics associated with this syndrome.
D. Growth hormone stimulation of IGF-1 secretion is an important
aspect of its action.
A. ACTH acts by activation of adenylate cyclase and production of
cAMP. Inhibition of cAMP breakdown synergistically increases the
intracellular response to this hormone.