A 52-year-old man presents with progressive facial coarsening, jaw enlargement, and deepening of voice over the past 8 years. His wife reports he now snores loudly and frequently stops breathing during sleep. On examination, the structure marked **A** in the diagram is evident, along with macroglossia and thickened skin. His serum IGF-1 is elevated at 3.2 times the upper limit of normal. An oral glucose tolerance test shows a GH level of 3.5 ng/mL after 75g glucose load. MRI pituitary reveals a 1.8 cm sellar mass. Which of the following is the most likely diagnosis?
A. Gigantism from a growth hormone-secreting adenoma in childhood
B. Acromegaly from a pituitary somatotroph adenoma
C. Cushing syndrome with secondary hypertension and facial plethora
D. Thyroid hormone excess causing facial edema and prognathism
Explanation
Why "Acromegaly from a pituitary somatotroph adenoma" is right
The clinical presentation of insidious somatic overgrowth over 8 years with characteristic coarse facies, prognathism (structure A), macroglossia, obstructive sleep apnea, elevated IGF-1, failure of GH suppression to <1 ng/mL on OGTT (GH = 3.5 ng/mL), and a sellar adenoma on MRI is pathognomonic for acromegaly. The anchor feature—coarse facies with prognathism—is the hallmark facial phenotype resulting from chronic GH and IGF-1 excess from a pituitary somatotroph adenoma. This is the most common cause of acromegaly (>95% of cases). The delayed diagnosis (7–10 years is typical) reflects the insidious nature of the disease.
Why each distractor is wrong
Gigantism from a growth hormone-secreting adenoma in childhood: Gigantism occurs when GH excess begins before epiphyseal closure (childhood/adolescence), resulting in tall stature and proportionate overgrowth. This patient is 52 years old with an 8-year history—the disease began in adulthood, making this acromegaly, not gigantism. Gigantism and acromegaly are the same pathophysiology but different age of onset.
Thyroid hormone excess causing facial edema and prognathism: Hyperthyroidism causes facial flushing, lid retraction, and exophthalmos (Graves disease), not prognathism or coarse facies. Thyroid hormone does not cause jaw enlargement, macroglossia, or failure of GH suppression on OGTT. The elevated IGF-1 and abnormal GH dynamics rule this out.
Cushing syndrome with secondary hypertension and facial plethora: Cushing syndrome presents with moon facies, plethora, hirsutism, and proximal myopathy, but NOT prognathism, macroglossia, or acral enlargement. GH is suppressed in Cushing syndrome, not elevated. The elevated IGF-1 and failure of GH suppression are incompatible with this diagnosis.
High-YieldNEET PG
Acromegaly = insidious GH excess in adulthood → coarse facies + prognathism + macroglossia + acral enlargement + sleep apnea; diagnosis confirmed by elevated IGF-1 + failure of GH suppression on OGTT; pituitary somatotroph adenoma is the cause in >95% of cases.
Endocrine Society 2024; Williams Textbook of Endocrinology
Practice similar questions
Sign up free to access AI-powered MCQ practice with detailed explanations and adaptive learning.
