To the Editor. —
Sundbeck et al1 in their unsuccessful search for the causes of a low thyrotropin level in the elderly confined attention to the thyroid gland. A low thyrotropin level, however, is also a feature of panic disorder, where 22% of patients have been shown to have an undetectable level.2 This could conceivably be linked to the concomitantly elevated level of epinephrine in this disease,3,4 as its interactions with thyroid hormones have been extensively documented.5Thus, the levels in question may have been secondary not to thyrotoxicosis, but to adrenotoxicosis. Studies of adrenal function might provide an answer to this interesting question.