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Subclinical
hypothyroidism may spontaneously remit months or years after diagnosis
The background of the study. Subclinical hypothyroidism,
defined as a high serum thyrotropin (TSH) and a normal serum free
thyroxine (T4) concentration, is the most common disorder of thyroid
function. Once detected, it may disappear, persist, or progress
to overt hypothyroidism. The time course of disappearance of subclinical
hypothyroidism was determined in this study.
How the study was done. The study subjects were 40 patients with subclinical hypothyroidism whose serum TSH concentrations decreased to normal during follow-up. They were part of a group of 107 patients with subclinical hypothyroidism that had persisted for 1 to 3 months, after which they were studied at regular intervals for up to 72 months. Among the other 67 patients, 28 had progression to overt hypothyroidism during follow up, and 39 had persistent subclinical hypothyroidism.
The results of the study. Among the 40 patients whose serum TSH concentration was normal later, 3 had a goiter, 15 had symptoms of hypothyroidism, and 24 had high serum concentrations of antithyroid peroxidase antibodies. At base line, their average serum TSH concentration was 7.5 mU/L (normal, 0.4 to 4.0).
Their serum TSH concentrations fell to normal in 6 to 60 months. The fall occurred during the first year of follow-up in 38 percent, the second year in 30 percent, the third year in 7 percent, and the fourth or fifth year in 25 percent. There was no correlation between age, sex, or serum antithyroid peroxidase antibody concentration at base line and the final serum TSH concentration.
The conclusions of the study. Among patients with subclinical hypothyroidism, serum TSH concentrations may fall to normal spontaneously as long as five years after diagnosis.
The original article. Diez JJ, Iglesias P, Burman
KD. Spontaneous normalization of thyrotropin concentrations in patients
with subclinical hypothyroidism. J Clin Endocrinol Metab 2005;90:4124-7.
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| Thyroid Digest Index | | | November 2005 Thyroid Digest |
