Serum thyroid hormone values and counts
of blood eosinophils and monocytes distinguish between Graves' disease
and thyroiditis
(November 2002)
The background of the study.
Silent (painless) thyroiditis and Graves' disease are common causes
of thyrotoxicosis, and distinguishing between them is important
because treatment differs. In this study the efficacy of measurements
of the ratio of free triiodothyronine (T3) to free thyroxine (T4)
in serum and the ratio of eosinophil cells to monocyte cells in
blood to differentiate between the two disorders was evaluated.
How the study was done.
The study subjects were 111 patients with thyrotoxicosis, of whom
69 had Graves' disease, 21 had silent thyroiditis, and 21 had subacute
(painful) thyroiditis. All the patients had high serum free T3 and
free T4 concentrations. The diagnoses were based on standard criteria,
including measurements of thyrotropin receptor antibodies and thyroid
radioiodine uptake.
The results of the study.
The mean serum free T3 and free T4 concentrations were higher in
the patients with Graves' disease, as compared with the values in
the patients with painless thyroiditis or subacute thyroiditis.
The mean ratio of serum free T3 to free T4 was higher in the patients
with Graves' disease (0.40±0.09) than in the patients with
either painless thyroiditis (0.30±0.07, P<0.01) or subacute
thyroiditis (0.34±0.06, P<0.01). Among the 28 patients with
thyrotoxicosis who had a ratio of serum free T3 to free T4 of <0.3,
79 percent had silent or subacute thyroiditis.
In the patients with Graves' disease, 3.5 percent of white blood
cells were eosinophils, as compared with 1.4 percent in the patients
with silent thyroiditis (P<0.01) and 1.1 percent in the patients
with subacute thyroiditis (P<0.01). The mean ratio of eosinophils
to monocytes was 0.8 in the patients with Graves' disease, 0.3 in
the patients with silent thyroiditis, and 0.2 in the patients with
subacute thyroiditis (P<0.01).
The conclusions of the study.
Measurements of the ratio of free T3 to free T4 in serum and the
ratio of eosinophils to monocytes in blood help to distinguish between
Graves' disease and silent thyroiditis or subacute thyroiditis as
causes of thyrotoxicosis.
The original article.
Izumi Y, Hidaka Y, Tada H, Takano T, Kashiwai T, Tatsumi K, Ichihara
K, Amino N. Simple and practical parameters for differentiation
between destruction-induced thyrotoxicosis and Graves' thyrotoxicosis.
Clin Endocrinol 2002;57:51-8.
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