Pituitary Tumor: Causes, Symptoms, Diagnosis, and Treatment — Overview, Diagnosis & Treatment Options | MyMedicPlus

Pituitary tumors — predominantly pituitary adenomas — are the most common tumors of the sellar region, accounting for approximately 15% of all intracranial neoplasms. They arise from cells of the anterior pituitary gland and are classified by size (microadenoma <10 mm, macroadenoma ≥10 mm) and by hormonal secretory status. Functioning (secreting) adenomas produce excess hormones and include prolactinomas (most common, ~40%), somatotroph adenomas (GH excess causing acromegaly or gigantism, ~20%), corticotroph adenomas (ACTH excess causing Cushing's disease, ~10%), thyrotroph adenomas (TSH excess, rare), and gonadotroph adenomas (FSH/LH excess, uncommon). Non-functioning adenomas (~30%) cause symptoms through mass effect. True pituitary carcinomas are exceedingly rare (<0.5%). Craniopharyngiomas, meningiomas, and Rathke's cleft cysts are other sellar region tumors but are distinct from pituitary adenomas.

Most pituitary adenomas are sporadic with no identifiable genetic cause. Somatic mutations in the GNAS gene (encoding the Gs-alpha protein) are found in approximately 40% of somatotroph adenomas. Germline mutations causing hereditary pituitary tumors include MEN1 (multiple endocrine neoplasia type 1, caused by MEN1 gene mutation) — which predisposes to pituitary, parathyroid, and pancreatic tumors — and MEN4 (CDKN1B mutation). Familial isolated pituitary adenoma (FIPA) is associated with AIP gene mutations, particularly predisposing to somatotroph and prolactin-secreting adenomas presenting at a younger age. Carney complex (PRKAR1A mutation) includes GH-secreting adenomas. X-linked acrogigantism (XLAG) from GPR101 microduplication causes early childhood gigantism. The majority of sporadic cases have no identified predisposing mutation. There are no established modifiable environmental risk factors for pituitary adenomas.

Symptoms arise from two mechanisms: hormonal hypersecretion (functioning adenomas) and local mass effect (both functioning and non-functioning macroadenomas). Prolactinoma: amenorrhea, galactorrhea, and infertility in women; hypogonadism, erectile dysfunction, and infertility in men; in both sexes, headache and visual disturbance if large. Acromegaly/gigantism (GH excess): insidious coarsening of facial features, enlargement of hands and feet, prognathism, macroglossia, hyperhidrosis, oily skin, arthropathy, sleep apnea, and hypertension. Cushing's disease (ACTH excess): central obesity, moon face, buffalo hump, purple striae, proximal myopathy, hypertension, glucose intolerance, hirsutism, and osteoporosis. Mass effect (all large adenomas): bitemporal hemianopia (the classic visual field defect from chiasmal compression), headache, and hypopituitarism (deficiency of GH, TSH, ACTH, LH/FSH, or ADH). Pituitary apoplexy — sudden hemorrhage into an adenoma — presents as a thunderclap headache, diplopia, and acute visual loss requiring emergency treatment.

Diagnosis combines biochemical hormone assessment and neuroimaging. For suspected prolactinoma, serum prolactin measurement is the key test; levels >200 ng/mL are virtually diagnostic. For Cushing's disease: 24-hour urinary free cortisol, late-night salivary cortisol, 1-mg overnight dexamethasone suppression test, and CRH stimulation test. For acromegaly: serum IGF-1 (insulin-like growth factor 1) is the primary screening test; confirmation by oral glucose tolerance test (OGTT) showing failure of GH suppression to <1 ng/mL. Pituitary function panel (TSH, free T4, FSH, LH, testosterone in men, estradiol in women, IGF-1, prolactin, cortisol) assesses panhypopituitarism. MRI of the brain with dedicated pituitary protocol using gadolinium contrast is the gold standard imaging modality — offering superior soft tissue resolution of the sella turcica and cavernous sinus. Formal visual field testing (automated perimetry) is mandatory for macroadenomas with suprasellar extension. Inferior petrosal sinus sampling (IPSS) is used to distinguish pituitary-source Cushing's disease from ectopic ACTH production.

Treatment is tailored to tumor type, size, and patient factors. Prolactinomas: first-line treatment is medical therapy with dopamine agonists — cabergoline (preferred due to higher efficacy and tolerability; dose 0.5–3 mg/week) or bromocriptine. Dopamine agonists normalize prolactin and reduce tumor size in >85% of patients, often rendering surgery unnecessary. Surgery is reserved for drug-resistant or intolerant cases. Non-functioning macroadenomas and clinically significant GH/ACTH-secreting adenomas: transsphenoidal adenomectomy is the primary treatment. Endoscopic endonasal transsphenoidal surgery (EETS) via the sphenoid sinus approach is now the standard surgical technique, offering superior visualization of the sella, higher rates of hormonal remission, and lower morbidity than transcranial approaches. Remission rates for Cushing's disease with experienced neurosurgeons reach 75–85%; for acromegaly, 60–80%. Medical therapy for acromegaly includes somatostatin analogues (octreotide LAR, lanreotide) and GH receptor antagonist (pegvisomant) for surgical non-responders. Pasireotide is used for Cushing's disease. Radiation therapy — fractionated stereotactic radiotherapy (SRT) or stereotactic radiosurgery (Gamma Knife) — is used for residual or recurrent disease after surgery, with hormonal control taking 5–10 years.

The prognosis for pituitary tumors is generally excellent given that the overwhelming majority are benign adenomas with no metastatic potential. Prolactinomas respond to dopamine agonist therapy (cabergoline) in over 85% of patients, achieving normalization of prolactin levels, tumor shrinkage, and restoration of gonadal function — many patients achieve durable remission that permits cautious drug withdrawal after 2 years of normal prolactin on MRI. For acromegaly, transsphenoidal surgery achieves biochemical remission (IGF-1 normalization and GH <1 ng/mL on OGTT) in 60–80% of microadenomas and 40–60% of macroadenomas at experienced neurosurgical centers; uncontrolled acromegaly is associated with reduced life expectancy due to cardiovascular, respiratory, and metabolic complications that normalize with disease control. Cushing's disease remission rates reach 75–85% after transsphenoidal surgery, but recurrence occurs in 15–20% of patients within 5 years, necessitating life-long biochemical and imaging surveillance. Non-functioning macroadenomas recur in 10–20% of cases by 10 years after surgery. Pituitary hormone deficiencies identified pre- or post-operatively require lifelong replacement therapy — hydrocortisone, levothyroxine, testosterone or estrogen, and growth hormone as appropriate — but do not adversely affect life expectancy when adequately managed. Radiation therapy achieves disease control in most residual or recurrent adenomas over 5–10 years. True pituitary carcinomas, while exceedingly rare, carry a median survival of 2–4 years despite aggressive treatment.

There are no established measures to prevent sporadic pituitary adenomas. Genetic counseling and germline testing (MEN1, AIP, CDKN1B) should be offered to patients with pituitary tumors at young age, multifocal pituitary disease, family history of pituitary tumors, or features of MEN1 syndrome (hyperparathyroidism, pancreatic neuroendocrine tumors). Post-operative surveillance includes serial pituitary MRI at 3–6 months, then annually for 3–5 years and thereafter based on tumor behavior. Hormonal assessment (prolactin, IGF-1, cortisol) is repeated post-operatively to confirm biochemical remission. Pituitary hormone deficiencies identified pre- or post-operatively require long-term hormonal replacement (hydrocortisone, levothyroxine, testosterone/estrogen, growth hormone). Patients on cabergoline for prolactinoma should have serial MRI; drug withdrawal may be attempted after 2 years of normal prolactin if MRI shows no residual tumor.

Sudden-onset severe headache with visual disturbance, diplopia, or acute vision loss in a known or suspected pituitary tumor patient represents pituitary apoplexy — a neuroendocrine emergency requiring immediate emergency evaluation and likely surgical decompression. Women with unexplained amenorrhea, galactorrhea, and infertility should have serum prolactin and pituitary MRI. Men with hypogonadism, low libido, or infertility unresponsive to routine evaluation need pituitary hormone assessment. Progressive visual field loss — particularly bitemporal hemianopia — requires urgent ophthalmological and neuroimaging assessment. Features of acromegaly (progressive enlargement of hands, feet, jaw) or Cushing's syndrome (rapid weight gain, bruising, striae, hypertension) in a patient who has not been evaluated should prompt endocrinology referral. Incidental pituitary lesions found on brain MRI (incidentalomas) need endocrine evaluation to exclude hormonal activity and ophthalmology if >10 mm.