Growth hormone excess from a pituitary somatotroph adenoma; insidious enlargement of soft tissues, hands, feet, and jaw.
Also known as: acromegaly, gigantism, growth hormone-secreting adenoma, GH excess, IGF-1 excess
Overview
Chronic disease caused by sustained hypersecretion of growth hormone (GH) and consequent elevation of insulin-like growth factor 1 (IGF-1), almost always from a pituitary somatotroph adenoma. When onset is before epiphyseal closure (children), it produces gigantism; after closure, it produces acromegaly.
Epidemiology
Prevalence ~60 per million; incidence 3-4 per million per year. Equal sex distribution. Mean age at diagnosis 40-50 — typically presenting after 7-10 years of symptoms. Mortality 2-3× background if untreated, primarily from cardiovascular disease.
Try two board-style Acromegaly questions
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Question 1EndocrineMedium
A 48-year-old man presents to his primary care provider complaining that his wedding ring no longer fits and his shoe size has increased two sizes over the past 3 years. He also reports headaches, excessive sweating, and new snoring. On examination he has prominent supraorbital ridges, an enlarged jaw with widely spaced teeth, and large fleshy hands. Random serum insulin-like growth factor-1 (IGF-1) is markedly elevated, and growth hormone fails to suppress after a 75-gram oral glucose load. Which of the following is the most likely diagnosis?
APituitary somatotroph adenoma
BPituitary corticotroph adenoma
CPrimary hypothyroidism
DSevere insulin resistance syndrome
Reveal answer & full explanation
Correct answer: A — Pituitary somatotroph adenoma
APituitary somatotroph adenoma✓
BPituitary corticotroph adenoma
CPrimary hypothyroidism
DSevere insulin resistance syndrome
Why pituitary somatotroph adenoma is correct
This patient demonstrates the classic adult presentation of acromegaly: enlargement of acral parts (hands, feet, jaw), frontal bossing, macroglossia, and soft tissue overgrowth occurring after epiphyseal closure — almost always due to a growth hormone-secreting pituitary somatotroph adenoma
Diagnostic gold standard is failure of growth hormone to suppress below 1 ng/mL after a 75-gram oral glucose tolerance test, combined with an elevated age-adjusted IGF-1 — both present in this patient
Pituitary MRI is then obtained to localize the adenoma; first-line therapy is transsphenoidal resection
If growth hormone excess occurs before epiphyseal closure, the result is gigantism rather than acromegaly
Why the others are wrong
Pituitary corticotroph adenoma — (Cushing disease) produces central obesity, moon facies, purple striae, and proximal weakness from cortisol excess, not acral enlargement
Primary hypothyroidism — can cause a puffy, coarse appearance but does not enlarge the jaw or hands or elevate IGF-1; TSH would be high and free T4 low
Severe insulin resistance syndrome — can produce some acromegaloid soft-tissue features (pseudoacromegaly) but with normal GH and IGF-1 levels and a normal glucose suppression test
Question 2EndocrineMedium
A 48-year-old man reports that his hands and feet have enlarged over the past several years, requiring larger gloves and shoes. He has coarsened facial features, jaw prognathism, and a prominent brow. He was recently diagnosed with type 2 diabetes mellitus and hypertension. A serum IGF-1 level is elevated for his age and sex. Which test should be ordered to confirm the diagnosis?
AOral glucose tolerance test with serial growth hormone measurement
BRandom serum growth hormone level
C24-hour urinary free cortisol
DHigh-dose dexamethasone suppression test
Reveal answer & full explanation
Correct answer: A — Oral glucose tolerance test with serial growth hormone measurement
AOral glucose tolerance test with serial growth hormone measurement✓
BRandom serum growth hormone level
C24-hour urinary free cortisol
DHigh-dose dexamethasone suppression test
Why Oral glucose tolerance test with serial growth hormone measurement is correct
Acromegaly is caused in nearly all cases by a growth hormone (GH)-secreting pituitary adenoma
GH stimulates hepatic production of IGF-1, which mediates the somatic effects: acral enlargement, frontal bossing, prognathism, soft-tissue thickening, plus insulin resistance (diabetes) and hypertension
Because GH is secreted in pulses and is influenced by sleep, stress, and food, an isolated GH value is unreliable; IGF-1, which integrates GH activity over time, is the best screening test
Confirmation requires demonstrating that GH fails to suppress: an oral glucose tolerance test is administered and GH is measured serially; in normal individuals the glucose load suppresses GH to a low nadir, whereas in acromegaly GH remains inappropriately elevated
The oral glucose tolerance test with serial GH measurement is the confirmatory test, performed after a screening IGF-1 and before pituitary MRI to localize the adenoma
Why the others are wrong
B) Random serum growth hormone level — pulsatile secretion makes a single value uninterpretable for confirmation
C) 24-hour urinary free cortisol — this is the screening test for Cushing syndrome, a different cause of weight change and hypertension, not acromegaly
D) High-dose dexamethasone suppression test — used to localize the source of cortisol excess in Cushing syndrome and has no role in evaluating GH disorders
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Rare: ectopic GHRH from carcinoid or pancreatic NET, ectopic GH
Pathophysiology
Excess GH directly affects metabolism (insulin resistance, lipolysis) and stimulates hepatic IGF-1 production. IGF-1 drives growth of bone, cartilage, soft tissues, viscera, and vascular smooth muscle. Slow, progressive structural changes account for the delayed diagnosis. Pituitary mass effect may produce headache and bitemporal visual field defects.
Clinical presentation
Symptoms
Insidious change in hand/shoe/ring/hat size (often a key historical clue)
Prognathism / dental malocclusion isolated — Skeletal variant without acral changes or biochemical confirmation
Diagnostic workup
Diagnostic criteria
Elevated age/sex-adjusted IGF-1 + failure of GH to suppress below 1 ng/mL on OGTT + pituitary lesion on MRI.
Labs
Serum IGF-1 (age- and sex-adjusted) — first-line screen; elevated above reference range supports diagnosis
Oral glucose tolerance test (OGTT) with GH suppression — confirmatory; GH should suppress to <1 ng/mL (or <0.4 with ultrasensitive assay) after 75 g oral glucose; failure to suppress confirms acromegaly
Random GH alone is not reliable (pulsatile)
Prolactin (~25% of GH adenomas also secrete prolactin)
Full anterior pituitary panel: TSH, free T4, ACTH/cortisol, FSH/LH, testosterone/estradiol
Fasting glucose and A1c (insulin resistance, diabetes)
Lipid panel, BMP, calcium (MEN1 screen)
Imaging
Pituitary MRI with gadolinium — almost always shows macroadenoma (>1 cm)
Formal Humphrey visual field testing if optic chiasm compressed
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