Pituitary Adenoma: Causes, Symptoms and Treatment
A pituitary adenoma is a mostly benign tumor of the pituitary gland. It can produce hormones and affect various body functions.
Things worth knowing about "Pituitary adenoma"
A pituitary adenoma is a mostly benign tumor of the pituitary gland. It can produce hormones and affect various body functions.
What is a Pituitary Adenoma?
A pituitary adenoma is a mostly benign (non-cancerous) tumor that develops in the pituitary gland, a small, pea-sized gland located at the base of the brain. The pituitary gland plays a central role in regulating many vital hormones throughout the body. Pituitary adenomas are among the most common brain tumors, accounting for approximately 10–15% of all intracranial tumors. In the vast majority of cases, they do not spread to other parts of the body.
Types of Pituitary Adenomas
Pituitary adenomas are classified according to two main criteria:
By Size
- Microadenoma: Smaller than 10 mm. Often discovered incidentally during imaging studies performed for other reasons.
- Macroadenoma: Larger than 10 mm. May compress surrounding structures, most importantly the optic chiasm, leading to vision problems.
By Hormone Activity
- Functioning (secreting) adenomas: These tumors produce excess hormones, such as prolactin (prolactinoma), growth hormone (leading to acromegaly), or ACTH (leading to Cushing disease).
- Non-functioning (non-secreting) adenomas: These tumors do not produce active hormones and are often discovered due to symptoms caused by their size.
Causes and Risk Factors
The exact cause of most pituitary adenomas is not fully understood. They typically arise from spontaneous genetic changes in individual pituitary cells. In rare cases, they may occur as part of an inherited condition such as multiple endocrine neoplasia type 1 (MEN1). Known risk factors include:
- Family history of pituitary tumors (genetic predisposition)
- MEN1 syndrome or other hereditary endocrine disorders
- Rarely: previous radiation to the head region
Symptoms
Symptoms depend on whether the tumor produces hormones and how large it is:
Symptoms from Hormone Overproduction
- Prolactinoma: Milk production outside of breastfeeding, absent menstrual periods, infertility, reduced libido or erectile dysfunction
- Acromegaly (growth hormone adenoma): Enlargement of the hands, feet, and facial features; joint pain; diabetes
- Cushing disease (ACTH adenoma): Weight gain, moon face, high blood pressure, diabetes, skin changes
Symptoms from Mass Effect
- Headaches, often in the frontal or temporal region
- Visual disturbances, particularly bitemporal hemianopia (tunnel vision) caused by pressure on the optic chiasm
- Hormonal deficiency (hypopituitarism) due to compression of healthy pituitary tissue: fatigue, weight changes, loss of libido
Diagnosis
The diagnosis of a pituitary adenoma typically involves a combination of:
- Blood and urine tests: Measurement of hormone levels (e.g., prolactin, IGF-1, cortisol, TSH, LH, FSH)
- MRI (Magnetic Resonance Imaging): The gold standard for visualizing the size and location of the tumor
- Ophthalmological examination: Visual field testing to detect pressure on the optic chiasm
- Stimulation and suppression tests: For example, the dexamethasone suppression test when Cushing disease is suspected
Treatment
Treatment depends on the type, size, and hormone activity of the adenoma, as well as the overall health of the patient:
Medical Therapy
For prolactinomas, dopamine agonists (e.g., cabergoline, bromocriptine) are the first-line treatment. They reduce prolactin production and often significantly shrink the tumor.
Surgery
For most other types of adenomas, transsphenoidal surgery (performed through the nasal passages) is the standard approach. The goal is to remove the tumor while preserving as much healthy pituitary tissue as possible.
Radiation Therapy
Radiotherapy (e.g., Gamma Knife radiosurgery) is used when surgery is not possible or when the tumor has not been completely removed. It acts slowly and is often used as an adjunct to other treatments.
Watchful Waiting
Small, non-functioning microadenomas without symptoms are often initially monitored with regular MRI scans (so-called watchful waiting) rather than treated immediately.
Prognosis
The prognosis for pituitary adenomas is generally favorable. Most adenomas are benign, treatable, and not directly life-threatening. Following successful treatment, hormone levels can often normalize. Regular follow-up examinations are important, however, as recurrences can occur.
References
- Melmed S. et al. – Diagnosis and Treatment of Hyperprolactinemia: An Endocrine Society Clinical Practice Guideline. Journal of Clinical Endocrinology & Metabolism, 2011.
- Dekkers O.M. et al. – Epidemiology and Clinical Aspects of Pituitary Tumors. In: Endotext [Internet]. MDText.com, Inc.; updated 2022.
- Melmed S. – Pathogenesis of Pituitary Tumors. Nature Reviews Endocrinology, 2011.
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