October 30, 2010

PLAB Question 23

A 34 year old complains of fatigue and weight gain. On examination she is found to have dry skin and a bitemporal hemianopia.

The cause of her weight gain is most likely to be:

a) Pickwickian syndrome
b) Cushing's syndrome
c) affective disorder
d) Sjogren's syndrome
e) Laurence-Moon-Bardet-Biedl Syndrome
f) fibromyalgia
g) Stein-Leventhal Syndrome
h) secondary hypothyroidism
i) hypothalamic disorder
j) Carpenter's syndrome

The correct answer is H

Secondary hypothyroidism should be suspected when, in the setting of overt hypothyroidism, the TSH level is inappropriately low.

Concurrent amenorrhea, galactorrhea, postural hypotension, or visual field cut also suggests pituitary-hypothalamic pathology. Imaging of the sellar region is indicated.

Computed tomography (CT) scan is best for detection of small lesions within the sella; magnetic resonance imaging (MRI) is best for imaging the suprasellar region. TRH stimulation is sometimes used to confirm secondary hypothyroidism, but the test often fails to distinguish among secondary causes.

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