The level of circulating carcinoembryonic antigen (CEA) was measured in 148 patients with various thyroid diseases. A significantly high frequency of positive CEA was observed in hypothyroid patients with Hashimoto's disease, but the serum CEA levels were not correlated with the serum calcitonin concentrations in Hashimoto's disease. The CEA levels were inversely correlated with the serum T4 concentrations (P less than 0.001) and were positively correlated with the serum TSH concentrations (P less than 0.001), but not with the titers of serum antithyroid antibodies or the size of goiter in autoimmune thyroid disease. Moreover, the increase in CEA was significantly related to the duration of hypothyroidism (P less than 0.001). The high CEA levels in all hypothyroid patients decreased when the patients attained a euthyroid state after thyroid hormone therapy for 4-9 months. The gradual decrease in the serum CEA levels during treatment was roughly correlated with the decreases in serum cholesterol concentration and serum lactic dehydrogenase and glutamic oxalacetic transaminase activities. On Sephadex G-200 column chromatography of serum from hypothyroid patients, the CEA immunoreactivity, like purified standard CEA, was recovered in the large molecular weight fraction. These findings indicate that elevated CEA levels in hypothyroid patients do not necessarily indicate malignancy. CEA elevation in hypothyroidism may be caused by decreased degradation of CEA.

Four patients with Graves' disease whose hyperthyroidism was in remission following antithyroid therapy were studied without any treatment during and after pregnancy. In the 8-9th month of pregnancy, they were in a euthyroid state with serum levels of thyroxine (T4) of 18.9, 11.9, 11.2 and 14.5 mug/100 ml, triiodothyronine (T3) of 273, 190, 162 and 244 ng/100 ml and T3 resin sponge uptake (RT3U) of 22, 14, 19 and 16% respectively (normal pregnant range: T4, 7.0-15.0, T3 140-250, RT3U 15-25). At 1-3 months after delivery, hyperthyroidism recurred, as manifested by T4 levels of 17.2, 14.5, 16.7 and 21.7 mug/100 ml, T3 levels of 320, 225, 390 and 464 ng/100 ml and RT3U levels of 34, 34, 43, and 41% respectively (normal non-pregnant range: T4 5.0-12.0, T3 90-190, RT3U 24-37). The recurrence of hyperthyroidism was also demonstrated by serial measurements of serum free T4 and free T3. The thyroid function of all four patients returned spontaneously to the normal range at 4-6 months after delivery. One patient developed hypothyroidism for a short period before regaining the euthyroid state. The titers of serum anti-thyroid microsomal antibodies and levels of serum immunoglobulins decreased during pregnancy and increased transitorily at the time of hyperthyroidism after delivery. Similarly, increases in the levels of thyroid hormones, anti-thyroid antibodies and immunoglobulins were observed transitorily following spontaneous abortion after 4 months' pregnancy in one case. We suggest that the transient recurrence of hyperthyroidism in Graves' disease may be induced by immunological changes after delivery.

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