Lithium therapy can cause thyroiditis and
hyperthyroidism
(March 2002)
The background
of the study. Lithium carbonate has antithyroid
actions, and hypothyroidism and goiter are common side effects of
lithium therapy. This drug also has been associated with hyperthyroidism
caused by silent (painless) thyroiditis and by Graves' disease.
This study examined the relationship between lithium therapy and
hyperthyroidism caused by these two disorders.
How the study was done.
The study subjects were 100 consecutive patients with hyperthyroidism
caused by silent thyroiditis and 300 consecutive patients with hyperthyroidism
caused by Graves' disease. The number of patients with hyperthyroidism
and the total number of patients who had measurements of serum lithium
were determined, and the frequency of both causes of hyperthyroidism
among patients taking lithium was calculated.
The results of the study.
Among the 100 patients with hyperthyroidism caused by silent thyroiditis,
6 (6 percent) were taking or had recently taken lithium. Among the
300 patients with Graves' hyperthyroidism, 4 (1 percent) were taking
lithium. The incidence of lithium-associated silent thyroiditis
and hyperthyroidism was 1.3 cases per 1000 person-years, the incidence
of lithium-associated hyperthyroidism caused by Graves' disease
was 1.4 cases per 1000 person-years. The combined rate is higher
than the estimated rate of hyperthyroidism (0.3 to 1.2 cases per
1000 person-years) in the general population.
Nine additional patients with lithium-associated hyperthyroidism
(7 with silent thyroiditis, 1 with Graves' hyperthyroidism, and
1 with toxic multinodular goiter) were identified by review of records
at the same hospital. The 13 patients with lithium-associated silent
thyroiditis and hyperthyroidism included 8 women and 5 men; their
mean age was 34 years. Thyroid size was no more than 2 times normal
in any patient. Thyroid 24-hour I-123 uptake values were low in
all patients. The hyperthyroidism subsided spontaneously in the
12 patients who were followed up.
The conclusions of the study.
Hyperthyroidism caused by silent thyroiditis is associated with
lithium therapy more often than is hyperthyroidism caused by Graves'
disease, but both are more common in lithium-treated patients than
in the general population.
The original article.
Miller KK, Daniels GH. Association between lithium use and thyrotoxicosis
caused by silent thyroiditis. Clin Endocrinol 2001;55:501-8.
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