Pituitary Microadenomas Clinical Presentation

Updated: Mar 23, 2018
  • Author: Bernard Corenblum, MD, FRCPC; Chief Editor: George T Griffing, MD  more...
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Presentation

History

Types of pituitary microadenomas

Nonsecreting incidentalomas usually have no associated symptoms. They are ordinarily found in people who have radiologic studies for other reasons (eg, headaches). Unlike macroadenomas, incidentalomas are too small to cause pressure-related symptoms such as headache, diplopia, or visual-field loss.

Prolactinomas may be asymptomatic if prolactin levels are only slightly elevated. In women, hyperprolactinemia may cause galactorrhea, oligorrhea/amenorrhea, decreased libido, or infertility. In men, hypogonadism, erectile dysfunction, and decreased libido may ensue. Galactorrhea is rare in men.

Corticotropin-secreting adenomas cause Cushing disease.

Growth hormone–secreting adenomas cause acromegaly.

Thyroid-stimulating hormone (TSH)–secreting adenomas are a very rare cause of hyperthyroidism, and the patient has a nonsuppressed serum TSH level.

Gonadotropin-secreting adenomas have been reported. The frequency is rare. Women may present with amenorrhea and a mismatch between estrogen and gonadotropin levels (eg, elevated gonadotropin levels despite normal or elevated levels estrogen levels without suppression of gonadotropins). [13] They may be misdiagnosed as having ovarian failure.

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Physical

Any physical abnormalities are caused by excessive hormone secretion (eg, galactorrhea due to hyperprolactinemia, acromegaly due to excessive growth hormone, corticotropin-mediated Cushing disease). Most microadenomas found incidentally on CT scan or MRI are clinically inactive.

Patients with prolactin-secreting adenomas may present with galactorrhea. Other causes of galactorrhea need to be excluded, such as hypothyroidism and chest wall lesions.

Growth hormone–secreting adenomas cause acromegaly with coarsening of facial features and increased width of the hands and feet. Progressive bony proliferation of the mandible both lengthens and thickens it, resulting in separation of the lower teeth and an underbite. Skin thickness is increased compared with age- and sex-matched controls (>2 mm in reproductive-aged women, >3 mm in men).

Corticotropin-secreting adenomas cause Cushing disease characterized by weight gain, primarily in the facial, nuchal, truncal, and girdle areas (ie, centripetal or "buffalo" obesity). Protein breakdown leads to thin, friable skin that bruises easily; this breakdown may form wide striae that are often purple. The protein breakdown often causes muscle weakness (proximal muscles more than distal muscles), wasting, and osteopenia with fragility fractures. Women often develop hirsutism. In children, growth is arrested.

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Causes

As with adenomas elsewhere, the likely cause of pituitary microadenomas is a local mutation leading to autonomous growth and/or secretion. A variety of tumor suppressor genes and oncogenes have been described in sporadic pituitary tumorigenesis. [14]

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