A 35-Year-Old Soldier With Galactorrhea and Amenorrhea

Ranjodh Singh Gill, MD

Disclosures

May 24, 2021

TSH levels are used to monitor the effectiveness of treatment in primary hypothyroidism and should be kept in the normal range, except in selected cases, such as thyroid cancer and pregnancy. Levels should be measured 5-6 weeks after the start of thyroid hormone replacement, because of the long half-life of thyroxine (1 week), and also should be measured when the dose is changed. If the dose is stable and the patient is euthyroid, TSH levels can be monitored annually.

Absorption of levothyroxine can be impaired by the concurrent intake of food and many drugs, particularly calcium, iron, sucralfate, and bile acid sequestrants. Patients should be counseled to take levothyroxine on an empty stomach, apart from food and interfering medications. Some unfiltered water supplies, such as well water, can also interfere with absorption because of high mineral content.

Patients should be informed that treatment is usually lifelong. The dose requirement of levothyroxine can change owing to weight gain or loss, which affects the volume of distribution; pregnancy; and the use of estrogen.

This patient's prescription for levothyroxine was refilled, and she was counseled to take it separately from food and other medications, especially multivitamin and iron supplements. At a follow-up visit 3 weeks later, she reported that she had lost 5 lb and her dry skin had improved. She was taking levothyroxine on waking before eating breakfast and had started to take the multivitamin supplement later in the day. She had discontinued the iron supplement. At a 3-month follow-up visit, she was clinically and biochemically euthyroid, with a normal prolactin level, and her menstrual period had recently started. MRI performed 2 weeks later showed that the pituitary mass had diminished to 2-3 mm in diameter.

Stress was assessed as a possible contributor to hyperprolactinemia in this patient. However, it was ruled out as the specific cause because stress-induced hyperprolactinemia is usually seen in acute settings, such as after a seizure activity or a serious illness requiring hospitalization, and tends to be milder in nature.

This patient's normal FSH and LH levels ruled out premature ovarian failure, which is characterized by elevated levels. Her normal BMI and the absence of a history of excessive exercise excluded the female athlete triad as a cause of amenorrhea. The triad is usually associated with malnutrition and a low BMI. A prolactinoma was indirectly ruled out, because the prolactin level normalized and the pituitary mass resolved with the treatment of hypothyroidism.

The resolution of the pituitary mass in response to hypothyroidism treatment indicates that the cause of this mass is lactotroph hyperplasia. Other causes of pituitary masses are unlikely, if not impossible. The normal insulin-like growth factor 1 level ruled out acromegaly. The normal FSH and LH levels excluded a gonadotropin-producing tumor. A TSH-secreting pituitary adenoma was not considered because it is associated with an elevated FT4 level and hyperthyroidism. In this patient, the TSH level was elevated but the FT4 level was low.

Cushing syndrome was excluded by the lack of characteristic features and the normal cortisol level. Although a morning cortisol measurement is not a standard test for screening, the clinical suspicion was very low. Thus, a workup for Cushing syndrome was not undertaken. Standard screening includes one or more of following: an overnight dexamethasone suppression test, midnight salivary cortisol measurement, or 24-hour urine free cortisol measurement.

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