Acromegaly vs Gigantism
How to tell Acromegaly and Gigantism apart when a board question makes them look alike.
Acromegaly is GH excess after epiphyseal closure with acral enlargement; gigantism is GH excess before closure with linear height growth.
Side by side
Growth hormone excess after epiphyseal closure causing enlarged hands, feet, jaw, coarse facial features, organomegaly, insulin resistance, headaches, and cardiomyopathy risk.
Growth hormone excess before epiphyseal closure causing excessive linear growth and very tall stature in children or adolescents.
Pituitary somatotroph adenoma raises GH and IGF-1 after growth plates are fused, causing acral and soft tissue overgrowth rather than taller stature.
GH and IGF-1 excess acts on open epiphyseal growth plates, increasing longitudinal bone growth.
Elevated IGF-1 and failure of oral glucose to suppress GH support acromegaly in an adult with acral enlargement.
Elevated IGF-1 and failure of GH suppression in a child with open growth plates and rapid linear growth support gigantism.
The trap
The hormone excess is identical (growth hormone, usually from a pituitary somatotroph adenoma), so the deciding feature is whether the patient's growth plates are open. Gigantism is GH excess before epiphyseal plate closure in childhood or adolescence, producing rapid linear height growth (vertical gigantism with extreme stature). Acromegaly is GH excess after epiphyseal plate closure in adulthood, producing growth of acral parts (hands, feet, jaw, frontal bossing, enlarged tongue, deepened voice, organomegaly, sleep apnea, carpal tunnel syndrome, insulin resistance and diabetes, hypertension, cardiomyopathy). Both elevate IGF-1 with non-suppressible GH on oral glucose tolerance test.
The repair move
For suspected GH excess, work three steps in order: (1) screen with IGF-1 level (better than random GH because GH is pulsatile); (2) confirm with oral glucose tolerance test (failure of GH to suppress below 1 ng/mL after 75 g glucose load is diagnostic); (3) localize with pituitary MRI to identify the somatotroph adenoma. Treat surgically (transsphenoidal resection is first-line for micro- and macroadenomas), with medical adjuncts when surgery is incomplete or contraindicated: somatostatin analogs (octreotide LAR, lanreotide) first-line medical therapy; pegvisomant (GH receptor antagonist) for refractory disease; cabergoline (dopamine agonist) for mild disease.
Try a free question
CoreAn adult reports increasing shoe and ring size, coarse facial features, jaw enlargement, headaches, elevated IGF-1, and failure of GH suppression after oral glucose. Which diagnosis is most likely?
Show answer and explanation
Answer: A. Acromegaly. Adult GH excess after epiphyseal closure causes acromegaly with acral enlargement and elevated IGF-1.
Why the other choices are tempting
- B. Gigantism requires GH excess before epiphyseal closure with excessive linear growth.
- C. Cushing disease causes cortisol excess with striae, central obesity, and proximal weakness.
- D. Graves disease causes thyrotoxicosis with thyroid-specific clues.
- E. Marfan syndrome causes inherited connective tissue features, not GH nonsuppression.
Flashcards
Tap a card to flip it.
What adult features point to acromegaly?
Enlarged hands, feet, jaw, coarse facial features, organomegaly, and insulin resistance point to acromegaly.
What child feature points to gigantism?
Excessive linear growth before epiphyseal closure points to gigantism.
Quick answers
What is the fastest way to tell Acromegaly from Gigantism?
Acromegaly is GH excess after epiphyseal closure with acral enlargement; gigantism is GH excess before closure with linear height growth.
What is the key clue for Acromegaly?
Growth hormone excess after epiphyseal closure causing enlarged hands, feet, jaw, coarse facial features, organomegaly, insulin resistance, headaches, and cardiomyopathy risk.
What is the key clue for Gigantism?
Growth hormone excess before epiphyseal closure causing excessive linear growth and very tall stature in children or adolescents.
What is the common trap with Acromegaly vs Gigantism?
The hormone excess is identical (growth hormone, usually from a pituitary somatotroph adenoma), so the deciding feature is whether the patient's growth plates are open. Gigantism is GH excess before epiphyseal plate closure in childhood or adolescence, producing rapid linear height growth (vertical gigantism with extreme stature). Acromegaly is GH excess after epiphyseal plate closure in adulthood, producing growth of acral parts (hands, feet, jaw, frontal bossing, enlarged tongue, deepened voice, organomegaly, sleep apnea, carpal tunnel syndrome, insulin resistance and diabetes, hypertension, cardiomyopathy). Both elevate IGF-1 with non-suppressible GH on oral glucose tolerance test.