A 42-year-old man presents to the outpatient clinic reporting chronic diffuse joint pain, increasing fatigue, and excessive sweating over the past year. He mentions that he recently had to purchase larger shoes and his wedding ring can no longer be worn. His medical history includes newly diagnosed type 2 diabetes mellitus and hypertension. Vital signs show a blood pressure of , a heart rate of , and a BMI of . Physical examination reveals coarse facial features, a prominent jaw, macroglossia, and enlarged, doughy hands. Initial laboratory testing reveals an elevated serum insulin-like growth factor 1 (IGF-1) concentration for his age and sex. Which of the following is the most appropriate next step in the diagnostic workup?
- Measurement of serum growth hormone concentration following an oral glucose loadAnswer
- BMagnetic resonance imaging of the brain with emphasis on the sella turcica
- CMeasurement of a random fasting serum growth hormone concentration
- DFormal automated visual field perimetry testing
- ETransthoracic echocardiography
Answer
Measurement of serum growth hormone concentration following an oral glucose load
The correct sequence for diagnosing acromegaly is step-wise. Following clinical suspicion, the initial screening test is an insulin-like growth factor 1 (IGF-1) level, which is elevated in this patient. Once an elevated IGF-1 level is identified, the diagnosis must be confirmed biochemically before proceeding to anatomical localization. The definitive confirmatory test is the oral glucose tolerance test (OGTT). In normal physiology, a glucose load suppresses GH secretion; in acromegaly, GH levels fail to suppress and remain elevated (typically ).
Step-by-Step Solution
Key Concept
Diagnostic sequencing for acromegaly requires clinical suspicion followed by an elevated IGF-1 (screening), failure to suppress GH following an oral glucose load (confirmation), and finally MRI of the brain (localization).