Thyroid dysfunction in isolated adrenocorticotropic hormone (ACTH) deficiency: case report and literature review

A case of isolated ACTH deficiency accompanying transient primary hypothyroidism was reported along with a review of literature on isolated ACTH deficiency in Japan with special reference to its association with thyroid function. Our case, a 56-year-old woman, developed somnolence and hypoglycemia due to isolated ACTH deficiency. She also had the features of hypothyroidism, namely mounding phenomenon, muscle rigidity, increased plasma myogenic enzymes and cold intolerance. Both free T3 and free T4 were decreased, and basal as well as TRH-stimulated TSH levels were abnormally high. Plasma thyroglobulin was increased and no anti-thyroid antibodies were detected. All thyroid related physical and biochemical abnormalities disappeared after hydrocortisone replacement. A review of the literature on 103 cases disclosed that more than half the cases with isolated ACTH deficiency had a high plasma level of TSH, basal and/or TRH-induced, while the antithyroid antibodies were reported to be positive in only 13 cases. In more than 70% of such cases, the abnormality in the pituitary-thyroid axis was transient and was reversed by glucocorticoid replacement. Our case and cases in the literature indicate that the interference of thyroid hormone synthesis and/or secretion by glucocorticoid deficiency per se is the major cause of thyroid dysfunction rather than associated autoimmune thyroid disease.