Introduction: Although the most common causes of hyperprolactinemia are prolactinoma and iatrogenic, another possible cause is severe primary hypothyroidism, in which the increase of prolactin is a cause of pituitary stimulation by TRH, and can be presented with pituitary hyperplasia.
Case report: A 31-year-old woman who comes to endocrinology clinic for hyperprolactinemia, which was detected by symptoms of amenorrheagalactorrhea. After normal pregnancy 4 years ago, she persisted with galactorrhea and menstrual irregularities; with persistence of secondary amenorrhea and hypercholesterolemia in the last year. Sporadic headaches, no visual disturbances. Mild cold intolerance and some drowsiness. bilateral galactorrhea to expression. Normal palpable thyroid. Mild dry and pale skin. Minor bradypsychia. MRI: intrasellar tumor 1.5×1.2×2.5 cm which expands to sella. Homogenous contrast uptake. Involvement of the pituitary stalk and optic chiasm without invasion of the same. Invasion right cavernous sinus. Free T4:<0.1 ng/dl, TSH: 684 μU/ml, PRL: 79 ng/ml. After checking the normality of the visual field, levothyroxine therapy was started at a dose of 100 μg/day. At 2 months of treatment, menstruation was restored although minimal galactorrhea persisted to the expression. At 6 months was repeated MRI, which was normal. At 20 m. became pregnant, requiring increase dose to 125 and then 150 μg/day. In the last months of pregnancy developed gestational diabetes and was controlled with diet only. She had a normal birth at term, not macrosomic and 6 months breastfeeding, menstruation recovery after the same; levothyroxine dose was reduced to 125, maintaining normal hormones.
Conclusions: In the study of hyperprolactinemia is required the determination of thyroid hormones, although imaging test is observed pituitary enlargement which can be considered as prolactinoma, because levothyroxine replacement therapy in cases of severe hypothyroidism to regularize both, hormone levels and pituitary hyperplasia, avoiding unnecessary treatments (dopamine agonist) or even neurosurgery.