What is a pituitary macroadenoma?

Understanding Pituitary Macroadenoma

A pituitary macroadenoma is a benign tumor of the pituitary gland that is 10 mm or larger in size, which can cause symptoms through mass effects on surrounding structures and/or hormonal imbalances due to excessive hormone production or pituitary dysfunction. 1

What Is the Pituitary Gland?

The pituitary gland is a small, pea-sized gland located at the base of the brain behind the bridge of the nose. Despite its small size, it plays a crucial role in regulating many bodily functions by producing hormones that control:

• Growth
• Thyroid function
• Adrenal function
• Reproductive functions
• Water regulation in the body

Pituitary Macroadenomas: Key Facts

Classification

• Size: Macroadenomas are ≥10 mm in diameter (compared to microadenomas which are <10 mm) 1, 2
• Function: Can be either functioning (hormone-producing) or non-functioning 2

Prevalence

• Clinically evident pituitary adenomas occur in approximately 1 in 1100 people 2
• Macroadenomas account for approximately 48% of all pituitary adenomas 2

Types Based on Hormone Production

1. Non-functioning adenomas (30% of pituitary adenomas) - do not produce excess hormones 2
2. Functioning adenomas - produce excess hormones:
   • Prolactinomas (53%) - produce excess prolactin 2
   • Somatotropinomas (12%) - produce excess growth hormone 2
   • Corticotropinomas (4%) - produce excess ACTH 2
   • Thyrotropinomas (1%) - produce excess TSH 1

Symptoms of Pituitary Macroadenomas

Mass Effect Symptoms

Due to the tumor pressing on surrounding structures:

• Visual problems (18-78% of patients) - typically visual field defects due to compression of the optic chiasm 2
• Headaches (17-75% of patients) 2
• Hypopituitarism (34-89% of patients) - decreased production of one or more pituitary hormones 2

Hormone-Related Symptoms

Depending on which hormones are affected:

1. Prolactin excess:

   • Women: Irregular or absent menstrual periods, infertility, milk production (galactorrhea)
   • Men: Decreased libido, erectile dysfunction, infertility 2

2. Growth hormone excess:

   • Adults: Acromegaly (enlargement of hands, feet, facial features)
   • Children: Gigantism (excessive height) 2

3. ACTH excess (Cushing's disease):

   • Weight gain (especially trunk)
   • Round face
   • High blood pressure
   • Diabetes
   • Mood changes 2

4. Hypopituitarism (hormone deficiencies):

   • Fatigue
   • Low blood pressure
   • Intolerance to cold
   • Sexual dysfunction
   • Infertility 3

Diagnosis

1. MRI of the pituitary gland - The gold standard imaging test 1
2. Hormonal evaluation - Blood tests to check for hormone excess or deficiency 1
3. Visual field testing - To assess for visual impairment if the tumor is near the optic chiasm 1

Treatment Options

Treatment depends on the type, size, and symptoms of the macroadenoma:

1. Surgery - Usually transsphenoidal (through the nose) surgery is the first-line treatment for most macroadenomas except prolactinomas 2

2. Medication:

   • Prolactinomas: Dopamine agonists (cabergoline or bromocriptine) are first-line treatment 2
   • Growth hormone-secreting tumors: Somatostatin analogs, dopamine agonists, or GH receptor antagonists 1
   • ACTH-secreting tumors: Medications like ketoconazole, mifepristone, or pasireotide 1

3. Radiation therapy - Used for incomplete tumor resection or recurrence 1

Long-term Monitoring

• Regular follow-up with endocrinology
• Periodic MRI scans
• Ongoing hormonal assessments
• Visual field testing when indicated 1

Prognosis

With appropriate treatment, many patients with pituitary macroadenomas have excellent outcomes. The prognosis depends on:

• Tumor size and invasiveness
• Hormone production
• Response to treatment
• Presence of hypopituitarism before treatment

Early diagnosis and treatment are important to prevent permanent damage to the pituitary gland and surrounding structures.