Microprolactinoma

Microprolactinoma is a clinical condition characterized by the presence of a small pituitary adenoma (tumor) that secretes excessive amounts of prolactin. Prolactin is a hormone primarily responsible for lactation in females following childbirth, but it also has various other functions in both sexes, including effects on metabolism, immune system regulation, and reproductive health. Microprolactinomas are defined by their size, being less than 10 millimeters in diameter, distinguishing them from larger prolactin-secreting tumors known as macroprolactinomas.

Symptoms and Diagnosis

The symptoms of microprolactinoma often relate to the hyperprolactinemia (excess prolactin in the blood) it causes. In women, common symptoms include galactorrhea (inappropriate lactation), amenorrhea (absence of menstrual periods), infertility, and osteoporosis. Men may experience decreased libido, erectile dysfunction, infertility, and less commonly, galactorrhea. Both sexes may also suffer from headaches and visual disturbances if the tumor compresses adjacent structures in the brain.

Diagnosis of microprolactinoma typically involves blood tests to measure prolactin levels, magnetic resonance imaging (MRI) of the pituitary gland to identify the presence and size of the adenoma, and possibly additional tests to assess pituitary gland function.

Treatment

Treatment options for microprolactinoma include medical, surgical, and sometimes observation, depending on the severity of symptoms and the tumor's behavior. The primary treatment is medical therapy with dopamine agonists such as bromocriptine or cabergoline, which are effective in lowering prolactin levels, reducing tumor size, and resolving symptoms in the majority of cases. Surgery is reserved for patients who cannot tolerate or do not respond to medical therapy. Observation, or "watchful waiting," may be appropriate for patients with asymptomatic microprolactinomas, as these tumors often do not grow and may even shrink without treatment.

Prognosis

The prognosis for individuals with microprolactinoma is generally excellent, especially with early diagnosis and treatment. Most patients experience a significant improvement in symptoms and a normalization of prolactin levels with appropriate therapy. Long-term follow-up is necessary to monitor for potential tumor growth or recurrence, particularly if medical therapy is discontinued.

Epidemiology

Microprolactinomas are the most common type of functioning pituitary adenoma. They are more frequently diagnosed in women than in men, likely due to the more apparent and earlier symptoms related to reproductive functions in females. The prevalence of microprolactinomas is estimated to be higher than clinically recognized, as many tumors are asymptomatic and may go undetected.