Adolescent secondary amenorrhea: Association with hypothalamic hypothyroidism

In adolescent girls, secondary amenorrhea can result from a variety of physiologic and psychologic disturbances. Previous reports associating amenorrhea and primary hypothyroidism have not distinguished between the alternative etiologic roles of thyroxine deficiency and hyperprolactinemia. We have evaluated two girls with secondary amenorrhea who had clinical and chemical evidence of hypothyroidism. Both had low basal T 4 values (0.8 and 3.8 μg/dl), calculated free T 4 (0.1 and 0.7 ng/dl), and T 3 (51 and 81 ng/dl). Both had undetectable basal TSH with normal TSH response to TRH. Basal FSH and LH values were normal, as was the response to LHRH. Basal prolactin levels were 6 and 14 ng/ml, respectively, and both girls had growth hormone responses of ≥15 ng/ml in response to insulin-induced hypoglycemia. Pituitary-adrenal function and reserve were also normal. In neither patient was there any historical, physical, or laboratory features compatible with anorexia nervosa. After treatment with 1-thyroxine, both girls had a resumption in menses. These two adolescent girls thus appear to have isolated hypothalamic hypothyroidism. The associated secondary amenorrhea demonstrates that thyroid deficiency alone, without hyperprolactinemia, can interfere with normal hypothalamic-pituitary-ovarian function.