Objective: To describe 3 different scenarios of reversible hypothyroidism in young patients with adrenal insufficiency. Methods: We present 3 case reports of patients with adrenal insufficiency - one with delayed puberty, the second with type 1 diabetes and poor weight gain, and the third with hypoglycemia-related seizures and glucocorticoid deficiency - who had biochemical evidence of hypothyroidism. Results: Our first patient (case 1) initially had a mildly elevated thyrotropin (thyroid-stimulating hormone or TSH) level and a normal free thyroxine (FT4) level that, on follow-up assessment, had progressed to persistent mild elevation of TSH and low FT 4 concentration. The other 2 patients (cases 2 and 3) had low FT 4 and mildly elevated TSH values at the time of diagnosis of adrenal insufficiency. In all 3 patients, the results of thyroid function tests normalized with use of physiologic doses of adrenal hormone replacement therapy, without thyroid hormone replacement. All 3 patients remained euthyroid after 4, 3, and 1 year of follow-up, respectively. Conclusion: These observations add insights into the complexities of the thyroadrenal interactions. These examples are important because thyroid hormone replacement in the setting of adrenal insufficiency could be unwarranted. © 2006 AACE.