Pituitary Adenoma

Pituitary adenomas are benign (non-cancerous) tumors that develop in the pituitary gland, often called the "master gland" because it controls other hormone-producing glands in the body. These tumors account for 10-15% of all brain tumors and can cause symptoms by producing excess hormones or by pressing on surrounding structures.

Quick Facts

  • Prevalence: Found in up to 20% of people on autopsy studies
  • Types: Functioning (hormone-producing) or non-functioning
  • Size: Microadenomas (<10mm) or macroadenomas (≥10mm)
  • Treatment: Often curable with surgery or medication

Overview

The pituitary gland is a pea-sized organ located at the base of the brain, just behind the bridge of the nose. Despite its small size, it plays a crucial role in regulating vital body functions and general well-being by secreting hormones that control other glands throughout the body. Pituitary adenomas are benign tumors that arise from the cells of the pituitary gland.

These tumors are relatively common, though many remain undiagnosed because they don't cause symptoms. They are classified based on their size (microadenomas less than 10mm, macroadenomas 10mm or larger) and whether they produce excess hormones (functioning) or not (non-functioning). While benign, they can cause significant health problems by disrupting hormone production or compressing nearby structures like the optic nerves.

The good news is that pituitary adenomas are usually treatable, and many people with these tumors lead normal, healthy lives. Treatment options have advanced significantly, with minimally invasive surgical techniques, effective medications, and targeted radiation therapy offering excellent outcomes for most patients. Early detection and appropriate treatment are key to preventing complications and maintaining quality of life.

Symptoms

Symptoms of pituitary adenomas vary depending on the tumor's size and whether it produces hormones:

Mass Effect Symptoms (From Tumor Pressure)

  • Headache - Often frontal or behind the eyes
  • Eye pain - From pressure on surrounding structures
  • Vision problems:
    • Peripheral vision loss (bitemporal hemianopsia)
    • Double vision
    • Blurred vision
    • Decreased visual acuity
  • Nausea - Often with headaches

Hormone-Related Symptoms

  • Muscle swelling - From growth hormone excess
  • Prolactinoma symptoms:
    • Women: Irregular periods, breast milk production, infertility
    • Men: Erectile dysfunction, decreased libido, breast enlargement
  • Growth hormone excess (acromegaly/gigantism):
    • Enlarged hands and feet
    • Facial changes (jaw protrusion, enlarged nose)
    • Joint pain
    • Excessive sweating
  • ACTH excess (Cushing's disease):
    • Weight gain (central obesity)
    • Purple stretch marks
    • Easy bruising
    • High blood pressure
    • Diabetes
  • TSH-secreting adenoma:
    • Rapid heartbeat
    • Weight loss
    • Nervousness
    • Heat intolerance

Hormone Deficiency Symptoms (Hypopituitarism)

  • Fatigue and weakness
  • Weight loss or gain
  • Decreased sex drive
  • Feeling cold
  • Decreased appetite
  • Facial puffiness
  • Anemia
  • Infertility
  • In children: Growth failure

Seek Immediate Medical Attention For:

  • Sudden severe headache
  • Sudden vision loss
  • Confusion or altered consciousness
  • Severe nausea and vomiting
  • Signs of pituitary apoplexy (bleeding into tumor)

Types of Pituitary Adenomas

Pituitary adenomas are classified by size and hormone production:

By Size

  • Microadenomas: Less than 10mm in diameter
    • Often found incidentally
    • May not cause symptoms
    • Less likely to cause vision problems
  • Macroadenomas: 10mm or larger
    • More likely to cause mass effect symptoms
    • Can compress optic chiasm
    • May invade surrounding structures

Functioning Adenomas (Hormone-Producing)

  • Prolactinomas (40%):
    • Most common functioning adenoma
    • Produce excess prolactin
    • Often respond well to medication
  • Growth hormone-secreting (20%):
    • Cause acromegaly in adults
    • Cause gigantism in children
    • Associated with serious complications
  • ACTH-secreting (15%):
    • Cause Cushing's disease
    • Usually microadenomas
    • Can be difficult to locate
  • TSH-secreting (<1%):
    • Very rare
    • Cause hyperthyroidism
    • Usually macroadenomas at diagnosis
  • FSH/LH-secreting (rare):
    • Usually non-functioning clinically
    • May cause reproductive issues

Non-Functioning Adenomas (25-30%)

  • Do not produce excess hormones
  • Often larger at diagnosis
  • Symptoms from mass effect only
  • May cause hormone deficiencies

Causes

The exact cause of most pituitary adenomas is unknown, but several factors have been identified:

Genetic Factors

  • Multiple Endocrine Neoplasia type 1 (MEN1):
    • Hereditary syndrome
    • 20-60% develop pituitary adenomas
    • Often multiple hormone-producing tumors
  • Carney complex:
    • Rare genetic disorder
    • Associated with growth hormone-producing adenomas
  • Familial isolated pituitary adenoma (FIPA):
    • Runs in families
    • AIP gene mutations in some cases
    • Earlier onset than sporadic cases
  • McCune-Albright syndrome:
    • Genetic mosaicism
    • Associated with growth hormone excess

Molecular Changes

  • Mutations in GNAS gene (growth hormone adenomas)
  • USP8 mutations (Cushing's disease)
  • Cell cycle dysregulation
  • Growth factor abnormalities

Hypothetical Risk Factors

  • Hormonal influences
  • Head trauma (controversial)
  • Previous radiation exposure
  • Estrogen exposure (debated)

Risk Factors

Most pituitary adenomas occur sporadically, but certain factors may increase risk:

Genetic Risk Factors

  • Family history of pituitary adenomas
  • MEN1 syndrome
  • Carney complex
  • FIPA syndrome
  • McCune-Albright syndrome

Demographics

  • Age: Can occur at any age, peak in 30s-40s
  • Gender:
    • Prolactinomas more common in women
    • Other types show no clear gender preference

Other Associations

  • Previous pituitary radiation (secondary adenomas)
  • Certain medications (controversial)
  • Pregnancy (may unmask prolactinomas)

Diagnosis

Diagnosis involves hormonal testing, imaging, and sometimes specialized procedures:

Clinical Evaluation

  • Detailed medical history
  • Physical examination
  • Visual field testing
  • Neurological examination

Hormonal Testing

  • Baseline hormone levels:
    • Prolactin
    • Growth hormone and IGF-1
    • ACTH and cortisol
    • TSH and thyroid hormones
    • FSH, LH, testosterone/estrogen
  • Dynamic testing:
    • Dexamethasone suppression test (Cushing's)
    • Oral glucose tolerance test (acromegaly)
    • Insulin tolerance test (hormone deficiencies)
    • CRH stimulation test

Imaging Studies

  • MRI with gadolinium:
    • Gold standard for pituitary imaging
    • Thin slice protocol through sella
    • Can detect microadenomas
    • Shows relationship to surrounding structures
  • CT scan:
    • If MRI contraindicated
    • Shows bony anatomy
    • Less sensitive for small tumors

Additional Testing

  • Inferior petrosal sinus sampling:
    • For Cushing's disease confirmation
    • Helps lateralize ACTH source
  • Visual field testing:
    • Formal perimetry
    • Documents optic pathway compression
  • Ophthalmologic examination:
    • Fundoscopy
    • Visual acuity
    • Color vision

Treatment

Treatment depends on tumor type, size, symptoms, and patient factors:

Medical Therapy

  • Prolactinomas:
    • Dopamine agonists (first-line):
      • Cabergoline (preferred)
      • Bromocriptine
    • Effective in >90% of cases
    • Can normalize prolactin and shrink tumor
  • Growth hormone adenomas:
    • Somatostatin analogs (octreotide, lanreotide)
    • Growth hormone receptor antagonist (pegvisomant)
    • Dopamine agonists (selected cases)
  • ACTH-secreting adenomas:
    • Ketoconazole
    • Metyrapone
    • Pasireotide
    • Mifepristone (for diabetes control)

Surgical Treatment

  • Transsphenoidal surgery:
    • Minimally invasive approach through nose
    • Endoscopic or microscopic techniques
    • First-line for most non-prolactin adenomas
    • Success rates: 70-90% for microadenomas
  • Transcranial surgery:
    • For large, invasive tumors
    • When transsphenoidal approach inadequate
    • Higher complication rate

Radiation Therapy

  • Stereotactic radiosurgery (Gamma Knife, CyberKnife):
    • Single high-dose treatment
    • For residual or recurrent tumors
    • Less damage to surrounding tissue
  • Fractionated radiation therapy:
    • Multiple smaller doses
    • For larger tumors near optic structures
  • Proton beam therapy:
    • Precise targeting
    • Limited availability

Hormone Replacement

  • For pituitary hormone deficiencies
  • May include:
    • Thyroid hormone
    • Cortisol
    • Sex hormones
    • Growth hormone
    • Desmopressin (for diabetes insipidus)

Observation

  • Small, non-functioning microadenomas
  • Asymptomatic patients
  • Regular MRI and hormone monitoring
  • Intervention if growth or symptoms develop

Complications

Untreated or severe pituitary adenomas can lead to various complications:

Vision Complications

  • Permanent vision loss
  • Bitemporal hemianopsia
  • Optic atrophy
  • Diplopia from cranial nerve palsy

Hormonal Complications

  • Hypopituitarism:
    • Adrenal insufficiency (life-threatening)
    • Hypothyroidism
    • Hypogonadism
    • Growth hormone deficiency
  • Hormone excess syndromes:
    • Cardiovascular disease (acromegaly)
    • Diabetes (Cushing's, acromegaly)
    • Osteoporosis
    • Hypertension

Acute Complications

  • Pituitary apoplexy:
    • Sudden hemorrhage or infarction
    • Severe headache, vision loss
    • Medical emergency
    • May require urgent surgery
  • Hydrocephalus:
    • From obstruction of CSF flow
    • Large tumors

Treatment Complications

  • Surgical:
    • CSF leak
    • Meningitis
    • Diabetes insipidus
    • Hypopituitarism
    • Nasal complications
  • Radiation:
    • Delayed hypopituitarism
    • Cognitive changes
    • Secondary tumors (rare)
    • Optic neuropathy

Prognosis

The outlook for pituitary adenomas is generally good with appropriate treatment:

Favorable Prognostic Factors

  • Small tumor size at diagnosis
  • Complete surgical resection
  • Response to medical therapy
  • Absence of invasion
  • Young age
  • Experienced treatment team

Cure Rates

  • Microadenomas: 70-90% surgical cure
  • Macroadenomas: 50-70% surgical cure
  • Prolactinomas: >90% control with medication
  • Cushing's disease: 65-90% remission
  • Acromegaly: 50-70% biochemical cure

Recurrence

  • Overall recurrence rate: 10-20% at 10 years
  • Higher for invasive tumors
  • Regular monitoring essential
  • Re-treatment often successful

Quality of Life

  • Most patients return to normal activities
  • May need lifelong hormone replacement
  • Regular follow-up required
  • Fertility often restored with treatment

When to See a Doctor

Seek medical attention for symptoms suggesting a pituitary adenoma:

Urgent Evaluation Needed

  • Progressive vision loss
  • Severe, persistent headaches
  • Sudden severe headache with vision changes
  • Signs of hormone excess:
    • Rapid changes in appearance
    • Unexplained weight gain
    • New diabetes or hypertension

Schedule an Appointment For

  • Irregular menstrual periods
  • Unexpected breast milk production
  • Erectile dysfunction or low libido
  • Enlarging hands, feet, or facial features
  • Persistent fatigue and weakness
  • Growth problems in children
  • Unexplained infertility

Follow-up Care

  • Post-surgery: 6-12 weeks, then annually
  • Medical therapy: Every 3-6 months initially
  • Observation: MRI every 6-12 months
  • Post-radiation: Annual hormone testing

Emergency Symptoms (Pituitary Apoplexy)

  • Sudden, severe headache
  • Sudden vision loss or double vision
  • Confusion or decreased consciousness
  • Severe nausea and vomiting
  • Stiff neck