Pituitary hyperplasia: an uncommon presentation of a common disease

Summary

A 21-year-old woman presented with amenorrhea, bilateral galactorrhea and fatigue. Visual acuity and visual fields were normal. Laboratory examination demonstrated hyperprolactinemia. Magnetic resonance imaging (MRI) of the pituitary showed a 19×17×12-mm sellar mass with supra- and parasellar extension, causing compression of the pituitary stalk and optic chiasm. Further examinations confirmed mild hyperprolactinemia, strongly elevated TSH (>500 mU/l), low free thyroxine (FT ₄), hypogonadotropic hypogonadism and secondary adrenal insufficiency. Hydrocortisone and l-T ₄ replacement therapy was started. Three months later, the galactorrhea had disappeared, thyroid function was normalized and MRI revealed regression of the pituitary enlargement, confirming the diagnosis of pituitary hyperplasia (PH) due to primary hypothyroidism. Subsequently, the menstrual cycle returned and the hypocortisolism normalized. This case demonstrates that severe primary hypothyroidism may have an unusual presentation and should be considered in the differential diagnosis of pituitary enlargement associated with moderate hyperprolactinemia.

Learning points

• One should always try to find one etiology as the common cause of all the clinical findings in a pathologic process.

• Amenorrhea, galactorrhea and fatigue may be the only presenting clinical manifestations of primary hypothyroidism.

• Not every patient with galactorrhea, hyperprolactinemia and a pituitary mass has a prolactinoma.

• Primary hypothyroidism should always be considered in the differential diagnosis of hyperprolactinemia associated with pituitary enlargement and pituitary hormone(s) deficiency(ies).

• When PH due to primary hypothyroidism is suspected, thyroid hormone replacement should be started and only regression of pituitary enlargement on MRI follow-up can confirm the diagnosis.

• Examination of thyroid function in patients with a pituitary mass may avoid unnecessary surgery.