Hypocortisolemia in Graves Hyperthyroidism

Objective: To assess the risk of concomitant adrenal sufficiency in 2 patients with Graves thyrotoxicosis.

Methods: We present the clinical course and laboratory findings of 2 patients with hyperthyroidism associated with low basal serum cortisol and briefly review the literature with regard to possible mechanisms of hypocortisolemia in thyrotoxic states.

Results: Two women aged 37 and 43 years with long-standing Graves disease presented with hyperthyroidism secondary to nonadherence to prescribed antithyroid medications. Both women also had symptoms suggestive of adrenal insufficiency including nausea, vomiting, and diffuse abdominal pain in Patient 1 and fatigue and hypotension in Patient 2. In both patients, physical examination findings were consistent with hyperthyroidism. Laboratory results of Patient 1 included the following: thyrotropin, <0.002 mIU/L; free thyroxine, >6 microg/dL; and total triiodothyronine, 539 ng/dL. Laboratory results of Patient 2 included the following: thyrotropin, <0.002 mIU/L; free thyroxine, <6 microg/dL; and total triiodothyronine, 539 ng/dL. Morning basal cortisol levels were 0.9 microg/dL in Patient 1 and 0.6 microg/dL in Patient 2. Because of the low basal serum cortisol levels, the patients underwent a high-dose (250 mcg) cosyntropin-stimulation test; however, both patients had adequate cortisol response. At 60 minutes, serum cortisol concentration was 31.4 microg/dL in Patient 1 and 25.5 microg/dL in Patient 2. After adequately treating the hyperthyroidism, basal cortisol levels in both patients returned to the reference range.

Conclusion: Symptomatic hypocortisolemia may be present in severe hyperthyroidism, and it resolves with adequate treatment of the hyperthyroidism.