A 34-year-old woman has had fatigue, weight gain, irregular menstrual cycles, and milky discharge from both breasts for 6 months.
Physical examination reveals a small goiter, dry skin, and bilateral expressible galactorrhea. Laboratory results include a negative pregnancy test, a serum thyroid-stimulating hormone of 43 1iU/mL, and a serum prolactin level of 55 ng/mL.
What is the most appropriate next step in the management of this patients hyperprolactinemia?
A. Remeasure serum prolactin
B. Start estrogen therapy
C. Start dopamine agonist therapy
D. Start levothyroxine therapy
E. Obtain an MRI of the pituitary gland

The correct answer is D
Educational Objectives
Recognize and manage hyperprolactinemia due to primary hypothyroidism.
There are many secondary causes of hyperprolactinemia that are not associated with pituitary tumor.
One of the most common secondary causes of hyperprolactinemia is primary hypothyroidism. Up to 30% of women with primary hypothyroidism have a mildly elevated prolactin level. The reason for this elevation in primary hypothyroidism is thought to be increased stimulation of the pituitary gland by thyrotropin-releasing hormone, the hypothalamic hormone that stimulates thyroid-stimulating hormone and prolactin secretion from the pituitary gland. As in other secondary causes of hyperprolactinemia, serum prolactin levels in primary hypothyroidism are less than 200 ng/mL.
Treatment of primary hypothyroidism with levothyroxine to normalize serum TSH levels will also normalize prolactin levels, and irregular menses and galactorrhea should resolve. No other treatment directed specifically at the prolactin level or the hypogonadism (for example, estrogen or dopamine agonists) is usually required. MRI is unnecessary unless the elevated prolactin levels do not resolve with levothyroxine therapy.