High free thyroid hormone and decreased thyrotropin in pregnant women at 12 weeks do not exclude hyperthyroidism in pregnancy, transient thyrotoxicosis in pregnancy, etc. Further examination is needed, and observation or medication will be given according to the findings.
In early pregnancy, serum thyrotropin may decrease physiologically due to increased secretion of chorionic gonadotropin. If accompanied by elevated serum free thyroxine, further tests for thyrotropin receptor antibody, anti-thyroid peroxidase antibody, thyroglobulin antibody and thyroid ultrasound should be performed to determine whether hyperthyroidism is present, and if hyperthyroidism is present, it should be treated aggressively.
If there is no history of autoimmune thyroid disease and thyroglobulin antibodies are normal, then a possible gestational thyrotoxicosis is considered and regular observation is required.
Therefore, in a pregnant woman with high free thyroid hormone and decreased thyrotropin at 12 weeks, further investigation in an endocrinologist is recommended.