A 42-year-old man presents to the clinic complaining of worsening headaches and excessive sweating over the past 14 months. He mentions that his wedding ring has become too tight to wear and his shoe size has recently increased. His blood pressure is 148/92 mm Hg, and his heart rate is 78/min. Physical examination reveals coarse facial features, macroglossia, and widened hands with thickened fingers. Visual field testing by confrontation is normal. Due to high clinical suspicion for acromegaly, a serum insulin-like growth factor-1 (IGF-1) level is obtained and returns markedly elevated for his age and sex. Which of the following is the most appropriate next step in the diagnostic workup?
- Measurement of serum growth hormone following an oral glucose loadCevap
- BMagnetic resonance imaging of the pituitary gland
- CMeasurement of a fasting random serum growth hormone level
- DComputed tomography of the chest and abdomen
- EMeasurement of serum growth hormone-releasing hormone level
Cevap
Measurement of serum growth hormone following an oral glucose load
The proper sequence for diagnosing acromegaly begins with measuring insulin-like growth factor-1 (IGF-1) because it has a long half-life and reflects integrated 24-hour growth hormone (GH) secretion. Once an elevated IGF-1 level suggests the diagnosis, it must be biochemically confirmed before anatomic imaging is obtained. The gold standard confirmatory test is the measurement of serum GH levels following a 75-g oral glucose load. In a healthy individual, a glucose load will suppress GH to very low levels. In a patient with acromegaly, GH secretion is autonomous and will fail to suppress. Only after biochemical confirmation should imaging (MRI of the pituitary) be performed.
Adım Adım Çözüm
Anahtar Kavram
The diagnostic sequencing for acromegaly requires biochemical confirmation with an oral glucose tolerance test (failure to suppress growth hormone) before proceeding to anatomic localization with pituitary MRI.