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Chapter 26: Introduction to Endocrinology: The Hypothalamic–Pituitary Axis

A 78-year-old woman has received GH injections from an antiaging clinic. She is likely to experience which of the following effects?

a. Growth of the long bones in her legs

b. Carpal tunnel syndrome

c. Blurred vision

d. Decreased hearing

e. A metallic taste

Answer is b. Side effects associated with the initiation of GH therapy in adults include peripheral edema, carpal tunnel syndrome, arthralgia, or myalgia, which occur most frequently in patients who are older or obese.

A 6-year-old boy is diagnosed with central or GnRH-dependent precocious puberty. He is being treated with nafarelin, a GnRH analog, as a nasal spray. GnRH analogs are effective in precocious puberty because they

a. downregulate GnRh receptors on pituitary gonadotropes.

b. block the action of testosterone on muscle cells.

c. stimulate testicular estrogen synthesis.

d. antagonize the effect of luteinizing hormone (LH).

e. antagonize the effect of GnRH release from the hypothalamus.

Answer is a. The intermittent release of GnRH is crucial for the proper synthesis and release of the gonadotropins; the continuous administration of GnRH leads to desensitization and downregulation of GnRH receptors on pituitary gonadotropes and forms the basis for the clinical use of long-acting GnRH agonists to suppress gonadotropin secretion.

A 20-year-old male cyclist is suspected of using performance-enhancing drugs. Although his urine testosterone concentration is elevated, his testosterone/epitestosterone (T/E) (a measure of exogenous testosterone administration) ratio is normal. He has achieved this state by the use of which of the following?

a. Estrogen

b. Progestin

c. Human chorionic gonadotropin (hCG)

d. Low dose testosterone

e. Growth hormone (GH)

Answer is c. The administration of hCG can stimulate testosterone secretion in males with normal Leydig cell function. Epitestosterone is an inactive epimer of testosterone secreted from the testes. The normal T/E ratio is approximately one. A ratio much larger than this would suggest the exogenous administration of testosterone. hCG administration would stimulate endogenous testosterone secretion and thus the T/E ratio would be close to one.

A 4-year-old boy with short stature is diagnosed with growth hormone (GH) ...

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