What conditions are associated with the pituitary gland making too much hormone?

Conditions Associated with Pituitary Hormone Hypersecretion

The main conditions associated with pituitary gland hormone hypersecretion are functioning pituitary adenomas, which include prolactinomas, growth hormone-secreting adenomas (causing acromegaly/gigantism), ACTH-secreting adenomas (causing Cushing's disease), and rarely TSH-secreting adenomas. 1, 2, 3

Types of Hyperfunctioning Pituitary Adenomas

1. Prolactinomas (32-66% of pituitary adenomas)

• Clinical presentation:
  • Women: Amenorrhea, galactorrhea, infertility, decreased libido
  • Men: Decreased libido, erectile dysfunction, infertility
  • Both: Mass effects with macroadenomas (headache, visual field defects)
• Diagnosis: Elevated serum prolactin levels
• Treatment:
  • First-line: Dopamine agonists (cabergoline, bromocriptine)
  • Surgery reserved for drug resistance or intolerance 2, 3

2. Growth Hormone-Secreting Adenomas (8-16% of adenomas)

• Clinical presentation:
  • Adults: Acromegaly (enlargement of hands, feet, facial features, soft tissue swelling)
  • Children: Gigantism
  • Metabolic complications: Diabetes, hypertension
• Diagnosis:
  • Elevated IGF-1 levels
  • Failure to suppress GH after oral glucose load (<1 μg/L)
  • Note: In adolescents, complete GH suppression may be difficult to achieve 1
• Treatment:
  • First-line: Transsphenoidal surgery
  • Medical therapy: Somatostatin analogs, GH receptor antagonist (pegvisomant), dopamine agonists 4, 2

3. ACTH-Secreting Adenomas (2-6% of adenomas)

• Clinical presentation: Cushing's disease
  • Central obesity, moon facies, buffalo hump
  • Hypertension, diabetes, osteoporosis
  • Proximal muscle weakness, easy bruising, striae
• Diagnosis:
  • Elevated 24-hour urinary free cortisol
  • Elevated late-night salivary cortisol
  • Failure to suppress cortisol with low-dose dexamethasone
  • Petrosal sinus sampling may be needed to confirm pituitary source
• Treatment:
  • First-line: Transsphenoidal surgery
  • Medical therapy: Ketoconazole, mifepristone, pasireotide 2, 3

4. TSH-Secreting Adenomas (1% of adenomas)

• Clinical presentation: Hyperthyroidism with inappropriately normal or elevated TSH
• Diagnosis: Elevated free T4 with normal/elevated TSH
• Treatment:
  • First-line: Surgery
  • Medical therapy: Somatostatin analogs 2

Special Considerations

Co-secretion of Multiple Hormones

• 65% of childhood-onset acromegaly cases have hyperprolactinemia
• 34-36% of children with gigantism have prolactin co-secretion
• TSH can also be co-secreted by somatotrophinomas but less frequently 1

Syndromic Associations

Several genetic syndromes are associated with pituitary adenomas:

• McCune-Albright syndrome
• Carney complex
• Multiple Endocrine Neoplasia type 1 (MEN1)
• MEN1-like diseases (MEN4, MEN5)
• Neurofibromatosis type 1 (with optic pathway gliomas) 1

Diagnostic Imaging

• MRI with high-resolution pituitary protocols is the gold standard
• Helps visualize microadenomas (<10mm) and macroadenomas (≥10mm)
• Contrast enhancement increases detection of small adenomas 1

Complications of Hyperfunctioning Adenomas

• Hypopituitarism (25-35% of cases) due to compression of normal pituitary tissue
• Visual field defects with macroadenomas that compress the optic chiasm
• Metabolic complications specific to each hormone excess syndrome 1, 3

Management Approach

1. Biochemical confirmation of hormone hypersecretion
2. MRI imaging to localize and characterize the adenoma
3. Assessment of other pituitary functions to detect hypopituitarism
4. Treatment based on adenoma type:
   • Prolactinomas: Medical therapy with dopamine agonists
   • Other functioning adenomas: Surgical resection as first-line
   • Medical therapy for residual disease or when surgery is contraindicated 4, 2, 3

Early diagnosis and treatment are crucial to prevent irreversible complications from hormone excess and mass effects of pituitary adenomas.