Growth Hormone Deficiency & Excess for PA
Growth Hormone Deficiency & Excess for the Physician Assistant Licensing Exam
Growth Hormone Deficiency (GHD)
- Etiology
- Congenital Causes: Genetic mutations affecting GH production or pituitary malformations (e.g., septo-optic dysplasia).
- Acquired Causes:
- Pituitary Tumors: Compression of somatotroph cells.
- Trauma or Surgery: Head injury or surgery affecting the hypothalamic-pituitary axis.
- Radiation: Damage from radiation therapy to the head or neck.
- Infiltrative Diseases: Conditions such as sarcoidosis or tuberculosis.
- Clinical Features
- Children: Short stature and delayed puberty due to reduced linear growth.
- Adults: Decreased muscle mass, increased fat (especially central obesity), osteoporosis, and cardiovascular risk (e.g., atherosclerosis).
- Diagnosis
- Low IGF-1 Levels: Reflect reduced GH activity.
- Stimulation Tests: Insulin tolerance test (ITT) or arginine stimulation test to assess GH secretion.
- MRI: Evaluate the pituitary for tumors or structural abnormalities.
- Treatment
- Recombinant GH Therapy: Used to promote growth in children and improve body composition in adults.
- Monitoring: Regular assessment of IGF-1 levels and adjustment of GH dosage.
Growth Hormone Excess (Acromegaly and Gigantism)
- Etiology
- Pituitary Adenoma: Most common cause of excess GH, usually a somatotroph adenoma.
- Ectopic GHRH Production: Rarely caused by tumors secreting GHRH (e.g., bronchial carcinoid).
- Clinical Features
- Acromegaly (Adults): Enlargement of hands, feet, jaw, and soft tissues (e.g., macroglossia). Cardiovascular complications (hypertension, heart failure) and insulin resistance.
- Gigantism (Children): Excessive linear growth before epiphyseal plate closure.
- Diagnosis
- Elevated IGF-1: Persistent elevation confirms GH excess.
- Oral Glucose Tolerance Test (OGTT): GH levels fail to suppress after glucose ingestion.
- MRI: Identify pituitary adenomas.
- Treatment
- Transsphenoidal Surgery: First-line treatment for pituitary adenomas.
- Medications: Somatostatin analogs (e.g., octreotide), GH receptor antagonists (e.g., pegvisomant), or dopamine agonists (e.g., cabergoline).
- Radiation Therapy: If surgery and medications fail to control GH levels.
Key Points
- Growth Hormone Deficiency (GHD):
- Presents with short stature in children, decreased muscle mass, and cardiovascular risk in adults.
- Diagnosis involves low IGF-1 and GH stimulation tests.
- Treated with recombinant GH therapy.
- Growth Hormone Excess:
- Caused by pituitary adenomas, leading to acromegaly in adults or gigantism in children.
- Diagnosed with elevated IGF-1 and OGTT.
- Treatment includes surgery, somatostatin analogs, and GH receptor antagonists.