q8 - guest1

[ArchivalUser]

A 45-year-old male complains of gradual weight gain over the past several years. His fingers have enlarged so
much that he can no longer wear his wedding ring. He sweats more than usual, and in particular, his hands are
constantly sweaty. He has also noticed a gradual coarsening of his facial features. An MRI reveals the presence
of a 1.5-cm tumor in the anterior pituitary. Which of the following endocrine abnormalities is likely to be present?


A. Decreased plasma growth hormone concentration

B. Decreased plasma IGF-1 concentration

C. Decreased plasma insulin concentration

D. Impaired glucose tolerance

E. Increased suppression of growth hormone secretion with oral glucose

[ArchivalUser]

D.?

[ArchivalUser]

yep D agreee...

[ArchivalUser]

D. Impaired glucose tolerance because of increasing plasma IGF-1 concentration

[ArchivalUser]

Explanation:

The correct answer is D. The patient probably has acromegaly due to a growth hormone-secreting adenoma in
the anterior pituitary. Hypersecretion of growth hormone in an adult will not cause an increase in stature, since
the epiphyses of long bones have already fused. However, overgrowth of bone in the face and skull produces
the characteristic protruding jaw and forehead observed in this disorder. Soft tissue proliferation leads to a
coarsening of facial features. The hands and feet are particularly affected, producing large and thickened
spade-like fingers and toes. Excessive growth hormone decreases the sensitivity of peripheral tissues to insulin
("anti-insulin" effect). This tends to raise blood glucose and produce a compensatory hyperinsulinemia (not
decreased plasma insulin, choice C) that functions to limit the hyperglycemia. Approximately 50% of patients
with acromegaly show impaired glucose tolerance.

Plasma levels of growth hormone (choice A) and IGF-1 (choice B) are both increased in acromegaly.

Administration of oral glucose does not suppress growth hormone in acromegaly as it does in normal individuals
(choice E).