ACROMEGALY

It is a disease of adult life characterized by the growth of bulk but not in the length of bone especially of the extremities from over-secretion of growth hormone after epiphyseal closure, due to adenoma of the anterior pituitary. Hypersecretion of growth hormone before puberty (before epiphyseal closure) produces gigantism. Most of the adenomas aremacroadenomas (> l cm in diameter).

Acromegaly is rarely caused by ectopic growth hormone-releasing hormone or growth hormone secreted by lymphoma, hypothalamic tumor, bronchial carcinoid, or a pancreatic tumor.

Growth hormone acts directly on some tissues, but most of its biological effects are because of stimulation of insulin-like growth factor (IGF-1) produced in the liver and other tissues.

CLINICAL FEATURES

DUE TO LOCAL EFFECTS OF ADENOMA

1. Due to increased intrasellar pressure

Headache & vomiting

2. Due to pressure upon adjacent optic chiasma and nerves causing

• Bitemporal hemianopia

• Cranial nerve palsy

• Hemiparesis

3. Due to destruction of the pituitary gland by the tumor

Hypothyroidism

Impotence

Amenorhea

DUE TO PITUITARY IIYPERSECRETION OF GROWTH HORMONE

Skeletal changes

• Large spade-like hands & large feet.

• Enlargement of the lower jaw (prognathism)

• Prominent supraorbital ridges with large
frontal sinuses.

• Increased hat size due to enlargement of
sinuses and skull bones.

• Spacing apart of teeth

• Arthropathy

• Over growth of vertebral bone can cause spinal
stenosis.

Soft tissue changes

• Tongue enlarged with difficulty in articulation. Hypertrophy of pharyngeal and laryngeal tissue causing obstructive sleep apnea.

• Thickening of lips and nose

• Thickening of soft tissue of hands & feet

• Thickening of skin, increased sweating, acne.

• Moist handshake ( due to sweating of palm)

• Myopathy

• Visceromegaly e.g. cardiomegaly, thyroid
goiter and hepatomegaly.

• Carpal tunnel syndrome.

• Colon polyps are common.

Metabolic effects

• Glucose intolerance (25%)

• Clinical diabetes mellitus (10%)

• Hypertension (50%)

• Weight gain due to increased mass of muscle and bone.

• Growth hormone secreting pituitary tumors usually cause hypogonadism due to secretion of prolactin or by suppression of normal pituitary tissue.

• Secondary hypothyroidism may occur.

COMPLICATIONS

• Hypopituitarism, hypertension, glucose intolerance or frank diabetes mellitus, cardiomegaly and cardiac
failure.

• Carpal tunnel syndrome, arthritis of hips, knees, and spine, spinal cord compression.

• Visual field defects.

• Acute loss of vision or cranial nerve palsy may occur if the tumor undergoes spontaneous hemorrhage and necrosis called pituitary

INVESTIGATIONS

L Fasting serum prolactin and insulin – like growth factor 1 (IGF- 1).

IGF-1 is elevated while serum prolactin is also elevated in 30% of patients.

3. Growth hormone level: clinical diagnosis must be confirmed by measuring growth hormone levels during glucose tolerance test (GTT).

4. Pituitary function tests: show partial or complete hypopuitarism.

5. X-rays: X- ray skull shows enlarged pituitary fossa & double floor may be seen due to greater enlargement of the gland on one side. X-rays of hand and feet may also show tufting of the terminal phalanges of fingers and toes.
A lateral view of foot shows increased thickness of the heel pad .

5. CT Scan & MRI to detect tumor extent. MRI is superior to CT scan.

MANAGEMENT

Untreated acromegaly results in markedly reduced survival with most of the deaths from heart failure, coronary artery disease, hypertension and colonic tumors. The aim of therapy is to reduce growth hormone level below 5mU/L.