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February 20, 2008

Thyroxine Monotherapy After Thyroidectomy: Coming Full Circle

Author Affiliations

Author Affiliation: Division of Endocrinology, Sinai Hospital of Baltimore, Johns Hopkins University School of Medicine, Baltimore, Maryland. Dr Cooper is also a Contributing Editor, JAMA.

JAMA. 2008;299(7):817-819. doi:10.1001/jama.299.7.817

It may be the experience of many clinicians, as it has been ours, that a very small group of patients with hypothyroidism are not entirely well on thyroxine replacement alone.1

The concept of hormone replacement therapy is commonly credited to Brown-Sequard, who in 1889 at age 72 years injected himself with an extract of dog testicles and noted enhanced vitality and mental acuity.2 The concept of “internal secretion” arose from these experiments, and soon thereafter Murray successfully treated myxedema with “juice” extracted from sheep thyroid glands.3 Replacement therapy with virtually all clinically relevant hormones has been possible since the middle of the 20th century. The challenge, however, is to administer these hormones in deficiency states in a way that precisely replicates the complex manner in which they are endogenously secreted. Insulin replacement in patients with type 1 diabetes is an obvious example of this difficulty. Even the most sophisticated patient using an external insulin pump and continuous glucose monitoring has difficulty mimicking normal insulin secretion without being subjected to potentially dangerous hypoglycemia.