Growth Hormone (GH) Excess
meduploader - 06-29-09 15:22

Childhood cases of GH excess are associated with gigantism (delayed epiphyseal closure leading to extremely tall stature); cases in adulthood are associated with acromegaly. Etiologies include the following:
Benign pituitary adenoma: In > 99% of cases, GH excess states are due to a GH-secreting pituitary adenoma. Typically they are macroadenomas (> 1 cm), as diagnosis is often delayed by as much as 10 years.
Iatrogenic: Treatment with human GH.
Ectopic GH or GHRH: Extremely rare; seen with lung carcinoma, carcinoid, and pancreatic islet cell tumors.
Cardiac: Hypertension (25%); cardiac hypertrophy.
Endocrine: Glucose intolerance (50%) or overt DM; hypercalciuria with nephrolithiasis (10%); hypogonadism (60% in females, 45% in males).
Constitutional: Heat intolerance, weight gain, fatigue.
Neurologic: Visual field cuts and headaches.
GI: ↑ colonic polyp frequency (order colonoscopy after diagnosis).
Other:
Soft tissue proliferation (enlargement of the hands and feet); coarsening of facial features.
Sweaty palms and soles.
Paresthesias (carpal tunnel syndrome is found in 70% of cases).
An ↑ in shoe, ring, or glove size.
Skin tags.
DIAGNOSIS
Labs: Random GH is not helpful. Elevated IGF-1 levels are the hallmark.
Glucose suppression: A GH > 2 ng/mL 60 minutes after a 100-g oral glucose load is diagnostic.
Radiology: MRI of the pituitary.
TREATMENT
Surgery: Transsphenoidal resection is usually first-line therapy and is curative in 60–80% of cases.
Medical: If GH excess persists after surgery, long-acting octreotide (a somatostatin analog) is usually added. If octreotide fails, pegvisomant, a GH receptor antagonist, will normalize IGF-1 levels in 80–90% of patients with acromegaly.
Radiotherapy: Used in patients with inadequate responses to surgical and medical therapy.
COMPLICATIONS
Hypopituitarism and cardiovascular effects (hypertension, CHF, CAD).