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Subclinical hyperthyroidism may persist or disappear spontaneously
The background of the study. Graves’ disease
and multinodular goiter are important causes of subclinical hyperthyroidism,
defined as a low serum thyrotropin (TSH) and a normal serum free
thyroxine (T4) concentration. In this study, patients with subclinical
hyperthyroidism caused by these two disorders were followed to determine
how often there was spontaneous improvement or progression to overt
hyperthyroidism.
How the study was done. The study subjects were
16 patients with subclinical hyperthyroidism, none of whom had any
clinical manifestations of hyperthyroidism. Seven patients (5 women,
2 men) had Graves’ disease, as defined by a high serum concentration
of thyrotropin (TSH)-receptor antibodies (TSH-RAb), and 9 patients
(7 women, 2 men) had a multinodular goiter, as defined by thyroid
ultrasonography and absence of serum TSH-RAb. The patients were
reevaluated and serum TSH, free thyroxine (T4), and TSH-RAb were
measured at varying intervals for up to 36 months.
The results of the study. Among the patients with
Graves’ disease, serum TSH concentrations increased to normal
in five in 3 to 19 months, and serum TSH-RAb values decreased to
normal or near normal in four, with little change in serum free
T4 concentrations. One patient had persistent subclinical hyperthyroidism.
One patient had a normal serum TSH concentration at 9 months, but
had overt hyperthyroidism at 36 months.
There was no change in thyroid function in the patients with a multinodular goiter, but one patient later had symptoms of hyperthyroidism and was treated with an antithyroid drug.
The conclusions of the study. Subclinical hyperthyroidism caused by Graves’ disease may disappear spontaneously or persist, whereas when caused by a multinodular goiter it usually persists.
The original article. Woeber KA. Observations concerning the natural history of subclinical hyperthyroidism. Thyroid 2005;15:687-91.
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| Thyroid Digest Index | | | November 2005 Thyroid Digest |
