Acromegaly and gigantism features

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Acromegaly and Gigantism: Clinical Features

Key Distinction

Both conditions result from excess Growth Hormone (GH) secretion, almost always due to a somatotroph (GH-secreting) pituitary adenoma. The timing relative to epiphyseal plate closure determines the syndrome:

	Gigantism	Acromegaly
Onset	Before puberty (open epiphyses)	After puberty (closed epiphyses)
Linear growth	Extraordinary height (proportionate)	No increase in height
Soft-tissue/bony changes	Present + height	Present without height

Etiology

Cause of GH excess (Harrison's 22e):

Source	Prevalence
Pituitary adenoma (all types)	~98%
- Densely/sparsely granulated GH cell adenoma	60%
- Mixed GH + PRL cell adenoma	25%
- Mammosomatotrope cell adenoma	10%
Extrapituitary tumor (pancreatic islet, lymphoma)	<1%
Excess GHRH (central: hypothalamic; peripheral: carcinoid, small-cell lung)	<1%

Associated syndromes include MEN-1 and McCune-Albright syndrome. GH co-secretes PRL in ~20-40% of cases (may cause hypogonadism and galactorrhea).

Gigantism - Features

Occurs when GH excess arises before epiphyseal fusion (childhood/adolescence)
The individual grows to extraordinary height - proportionate overall, but later develops acromegalic changes
If untreated, features of acromegaly superimpose as the patient ages
Increased length of long bones, enlarged head and feet (as shown below)

Features of acromegaly/gigantism - identical twins comparison showing increased height, enlarged head and feet

FIGURE: A 22-year-old man with gigantism (left) beside his identical twin (right). Note the increased height, prognathism, enlarged head, and enlarged feet. Clinical divergence began at age ~13. (Harrison's 22e, Fig. 392-7)

Acromegaly - Clinical Features

Onset is insidious (average delay of 7-10 years between onset and diagnosis). Features arise from GH/IGF-1 excess and local tumor mass effects.

1. Facial / Head Features

Coarsening of facial features (most characteristic)
Prognathism - jaw protrusion, leading to interdental separation and underbite
Frontal bossing - prominent supraorbital ridges / brow protrusion
Macroglossia - enlarged tongue
Enlarged nose, lips, and ears
Deepening of the voice (enlargement of larynx and sinuses)

Lateral profile of a patient with acromegaly showing coarse facial features (Scott-Brown's ENT, Fig. 82.3c)

2. Extremities

Enlarged hands and feet - "spade-like" or "shovel-like" hands; patients note increasing ring/glove/shoe size
Soft-tissue swelling of the hands and feet

Enlarged "spade-like" hands in acromegaly

Enlarged, broadened hands ("spade hands") in acromegaly (Scott-Brown's ENT, Fig. 82.3d)

3. Musculoskeletal

Degenerative osteoarthritis (vertebral changes, joint pain - arthralgia)
Myopathy - proximal muscle weakness
Kyphosis / vertebral changes
Carpal tunnel syndrome (median nerve compression from soft-tissue swelling)
Hearing loss (from bony changes)

4. Skin and Soft Tissue

Excess sweating (hyperhidrosis) - one of the most common symptoms
Hirsutism
Oily skin, acne-like lesions
Acanthosis nigricans
Skin tags (acrochordons)

5. Metabolic

Insulin resistance / Diabetes mellitus - GH is diabetogenic (anti-insulin effect); ~25% have abnormal glucose tolerance
Hypercalciuria (GH stimulates renal 1α-hydroxylase → increased vitamin D activation → increased calcium absorption)
Hyperprolactinemia in ~30% (co-secretion) - may cause galactorrhea in ~4% and hypogonadism

6. Cardiovascular (most common cause of death)

Hypertension
Cardiomegaly / cardiomyopathy
Arrhythmias
Congestive cardiac failure
Ischaemic heart disease and cerebrovascular disease
Premature cardiovascular disease is the leading cause of death

7. Respiratory

Obstructive sleep apnoea (OSA) - common; from macroglossia, soft-tissue hypertrophy, and jaw changes

8. Gastrointestinal

Colonic polyps (increased risk of colorectal neoplasia) - screening colonoscopy required at diagnosis
Multinodular thyroid enlargement

9. Neurological / Local Tumor Effects

Headaches (pituitary expansion)
Visual field defects - bitemporal hemianopia from optic chiasm compression by macroadenoma
Polyneuropathy (rare; described by Adams & Victor)

Summary Table (Scott-Brown's ENT, Table 84.5)

Domain	Symptoms	Signs	Complications
Musculoskeletal	Arthralgia, increased shoe/hand size	Enlarged hands/feet, myopathy, osteoarthritis, prognathism, macroglossia	Carpal tunnel syndrome, hearing loss
Cardiovascular	-	Hypertension, cardiomyopathy	Ischaemic heart disease, CCF, cerebrovascular disease
Respiratory	-	OSA signs	Obstructive sleep apnoea
Metabolic	Sweating, headaches	Coarse features, hirsutism	Diabetes mellitus, metabolic syndrome
GI	-	-	Colonic polyps
Visual	-	Visual field defects	Blindness (if untreated)

Diagnosis

IGF-1 level (age/sex matched) - elevated; best screening test
Oral glucose tolerance test (OGTT): GH fails to suppress to <1 μg/L after glucose load - confirmatory test
MRI pituitary: demonstrates adenoma in 98% of cases
Screen for associated conditions: diabetes, hypertension, OSA, colonic polyps, thyroid enlargement, cardiovascular disease

Treatment Overview

Surgery: Transsphenoidal resection (first-line for most patients); remission ~70% for microadenomas, <50% for macroadenomas
Somatostatin receptor ligands (SRLs): Octreotide, lanreotide - normalize GH/IGF-1 in ~50%
GH receptor antagonist: Pegvisomant - for refractory cases
Radiotherapy: Reserved for aggressive tumors not responding to surgery/medical therapy (slow response, 5-15 years; risk of hypopituitarism)

Sources: Harrison's Principles of Internal Medicine 22e; Scott-Brown's Otorhinolaryngology Head & Neck Surgery Vol. 1; Ganong's Review of Medical Physiology 26e; Tietz Textbook of Laboratory Medicine 7e

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