Anterior Pituitary Disorders (Growth Hormone Axis)

Adult Growth Hormone Deficiency (AGHD)

_{^{Pituitary adenomas, craniopharyngiomas, pituitary surgery, radiation, or head trauma causing panhypopituitarism.}}

Clinical Presentation: Decreased lean muscle mass, increased central/abdominal adiposity, reduced bone mineral density (osteopenia/osteoporosis), impaired exercise capacity, and severe fatigue.

Adult Growth Hormone Deficiency (AGHD): diagnostics

Insulin Tolerance Test (ITT)

Glucagon Stimulation Test

Serum IGF-1

Insulin Tolerance Test (ITT)

Gold standard provocative test (Peak GH < 5.1 ng/mL). Contraindicated in patients with seizure disorders or active ischemic heart disease.

Glucagon Stimulation Test

Preferred alternative if ITT is contraindicated.

Serum IGF-1

Screening tool and diagnostic confirmatory marker

Adult Growth Hormone Deficiency (AGHD): Pharmacotherapy

Somatropin (Recombinant Human Growth Hormone - rhGH)

Monitoring: _{^{Serum IGF-1 levels, fasting blood glucose (GH has anti-insulin/diabetogenic effects), and bone density.}}

_{^{Side Effects: Peripheral edema, arthralgia, myalgia, carpal tunnel syndrome, and hyperglycemia.}}

Somatropin

Administered via Subcutaneous (SC) injection, typically once daily at bedtime (mimicking natural nocturnal GH surges).

Gigantism

GH hypersecretion occurs before epiphyseal plate closure in children (long bone growth).

Acromegaly

GH hypersecretion occurs after epiphyseal plate closure in adults (enlarged hands/feet, coarsened facial features, spade-like fingers, prognathism).

Growth Hormone Excess: diagnostics

OGTT Failure (GH remains elevated > 1 ng/mL after a 75g glucose load) + Elevated serum IGF-1.

Growth Hormone Excess (Acromegaly vs. Gigantism): Pharmacotherapy

Somatostatin Analogs (First-Line Medical)

GH Receptor Antagonist

Dopamine Agonists

Somatostatin Analogs (First-Line Medical)

Octreotide, Lanreotide

• Inhibit GH secretion by binding to somatostatin receptors (SSTR2/SSTR5).

GH Receptor Antagonist

Pegvisomant

• Blocks functional GH receptor dimerization; decreases circulating IGF-1 levels (does not decrease GH levels or tumor size).

Dopamine Agonists

Cabergoline, Bromocriptine

• Paradoxically inhibit GH secretion in patients with acromegaly.

(GHD): Biochemical Marker, Gold Standard Diagnostic Test, Diagnostic Result, First-Line Drug, Target Mechanism, Key Metabolic Watchout

Primary Biochemical Marker: Low Serum IGF-1

Gold Standard Diagnostic Test: Insulin Tolerance Test

(ITT)

Diagnostic Result: Peak GH < 5.1 ng/mL during hypoglycemia

First-Line Drug: Somatropin (Subcutaneous rhGH)

Target Mechanism: Replaces missing endogenous GH

Key Metabolic Watchout: Hyperglycemia / Reduced insulin sensitivity

(GHD)Growth Hormone Excess (Acromegaly): Biochemical Marker, Gold Standard Diagnostic Test, Diagnostic Result, First-Line Drug, Target Mechanism, Key Metabolic Watchout

Primary Biochemical Marker: Elevated Serum IGF-1

Gold Standard Diagnostic Test: Oral Glucose Tolerance Test (OGTT)

Diagnostic Result: Failure of GH to suppress < 1 ng/mL post-glucose

First-Line Drug: Octreotide or Lanreotide (Somatostatin analogs)

Target Mechanism: Inhibits anterior pituitary release of GH

Key Metabolic Watchout: Hyperglycemia / Cholelithiasis (gallstones)