Practice Test 11

A patient with a sellar mass undergoes dynamic endocrine testing. After IV administration of synthetic TRH, serum TSH rises only minimally. However, when the patient is exposed to acute cold (10 minutes), a small but reproducible increase in TSH is still observed. MRI suggests partial compression of the pituitary stalk with preserved pituitary tissue.

Which explanation is most consistent with the observed pattern of neuroendocrine integration?

In a disorder affecting neuroendocrine integration, a patient has episodes of hypoglycemia with inappropriately low plasma epinephrine during symptomatic events. Imaging suggests impaired adrenal medullary function, while adrenal cortex structure appears intact. During a controlled hypoglycemic clamp, plasma cortisol rises appropriately but epinephrine does not.

Which response is most consistent with the described disruption of neural–endocrine communication?