What are the clinical features and management of pituitary adenomas in adults?

Clinical Features of Pituitary Adenomas in Adults

Classification and Epidemiology

Pituitary adenomas affect approximately 1 in 1,100 adults and are classified as microadenomas (<10 mm) or macroadenomas (≥10 mm), with roughly half falling into each category. 1

• Approximately 30% are nonfunctioning adenomas that do not produce hormones 1
• Prolactinomas account for 32-66% of all pituitary adenomas 2, 1
• Growth hormone-secreting tumors represent 8-16% 2
• ACTH-secreting tumors account for 2-6% 2
• TSH-secreting tumors are rare, representing approximately 1% 3, 2

Clinical Presentations by Tumor Type

Prolactinomas

Prolactinomas present differently based on sex, with women experiencing amenorrhea, galactorrhea, and infertility, while men develop loss of libido, erectile dysfunction, and hypogonadism. 3, 2

• In women: delayed or arrested puberty, growth failure, primary amenorrhea, galactorrhea, menstrual disturbances, or secondary amenorrhea 3
• In men: hypogonadism, decreased libido, erectile dysfunction, and gynecomastia 3
• Important pitfall: Check for macroprolactin in mildly elevated prolactin cases, as macroprolactinaemia occurs in 10-40% of adults with hyperprolactinaemia and has low biological activity 4
• Critical consideration: Perform serial dilutions in patients with large pituitary lesions but paradoxically normal or mildly elevated prolactin due to the "high-dose hook effect" where very high prolactin saturates immunoassays 4

Growth Hormone-Secreting Adenomas (Acromegaly)

Acromegaly presents with progressive enlargement of the lips, tongue, nose, hands, and feet, and is diagnosed by elevated insulin-like growth factor 1 levels and growth hormone levels. 2

• Causes acromegaly in adults and gigantism in children 1
• Accounts for 12% of pituitary adenomas 1

ACTH-Secreting Adenomas (Cushing Disease)

Cushing disease presents with obesity, hypertension, diabetes, and significant metabolic morbidity. 2

• Late-night salivary cortisol is the best screening test 2
• Petrosal sinus sampling for ACTH may be necessary to distinguish pituitary from ectopic sources 2
• Represents approximately 65% of all cases of hypercortisolism 2

TSH-Secreting Adenomas

TSH-secreting tumors cause secondary hyperthyroidism and are extremely rare, accounting for only 1% of pituitary adenomas. 3, 2

Mass Effect Symptoms

Macroadenomas commonly cause headache (17-75% of patients), visual field defects (18-78%), and hypopituitarism (34-89%). 1

• Headache is especially common with macroadenomas 3
• Visual disturbances including visual field defects and loss of central vision occur from compression of the optic chiasm 3
• Cranial nerve palsies (diplopia, ocular motility problems) result from compression of cranial nerves III, IV, or VI 3
• Visual deterioration is an urgent indication for surgical decompression 3, 5

Hypopituitarism Manifestations

Hypopituitarism from mass effect presents with multiple hormone deficiencies affecting growth, reproduction, thyroid, and adrenal function. 3

• Growth hormone deficiency causes growth failure or short stature 3
• Gonadotropin deficiency leads to delayed or arrested puberty 3
• TSH deficiency causes hypothyroidism with fatigue, cold intolerance, and weight gain 3
• ACTH deficiency results in hypocortisolism with fatigue, weakness, and hypotension 3

Nonfunctioning Pituitary Adenomas

Nonfunctioning adenomas represent 15-54% of adult pituitary adenomas and typically present with mass effects rather than hormonal symptoms. 3, 2

• Microadenomas are usually asymptomatic and discovered incidentally on imaging 3
• Macroadenomas present with headache, visual field defects, and hypopituitarism 3
• Central diabetes insipidus is extremely rare at diagnosis of nonfunctioning adenomas 6

Essential Diagnostic Evaluation

All patients with suspected pituitary adenomas require comprehensive endocrine evaluation for hormone hypersecretion, and those with macroadenomas need additional assessment for hypopituitarism and visual function. 1

• MRI with contrast is the imaging modality of choice for anatomical delineation 5
• Visual assessment including visual acuity, visual fields, and fundoscopy should be performed in all patients with macroadenomas 5
• Complete pituitary function testing for gonadal, thyroid, and adrenal function as well as prolactin and growth hormone secretion 7

Management Principles

For prolactinomas, dopamine agonists (cabergoline or bromocriptine) are first-line treatment, even for macroadenomas with visual compromise; for all other adenomas requiring treatment, transsphenoidal surgery is generally first-line therapy. 5, 8, 2, 1

• Cabergoline is FDA-approved for treatment of hyperprolactinemic disorders, either idiopathic or due to pituitary adenomas 8
• Transsphenoidal surgery is the technique of choice for growth hormone-secreting and ACTH-secreting adenomas 5
• Small, asymptomatic nonfunctioning adenomas and prolactinomas can be observed without immediate intervention 2, 9
• Post-operative MRI surveillance should occur at 3 and 6 months, then at 1,2,3, and 5 years 5