Diagnosis

The combination of a significantly elevated TSH with a suppressed FTI indicates hypothyroidism. Both anti-thyroid antibody tests are positive; in the setting of hypothyroidism with a firm, "lumpy" thyroid gland and a family history of thyroid problems, these findings are diagnostic for Hashimoto's thyroiditis.

Be aware that at some points in the course of Hashimoto's thyroiditis, active inflammation and tissue destruction in the thyroid may cause the release of excessive thyroid hormone from stored pools and such patients may present with hyperthyroidism. However, thyroid scanning will not show increased radio-iodine uptake and the remaining physical and lab findings will be similar to those in this case. Thus these patients can usually be distinguished from patients with Grave's disease without too much difficulty.

Diagnosis: Hashimoto's thyroiditis with hypothyroidism

Treatment and followup testing

Levothyroxine (112 痢/day) was begun with resolution of symptoms within two months. Followup laboratory studies showed:

                              Patient         Reference
T4, Total (S)                11.4 ug/dl        5 - 11.5
T3 resin uptake (S)            21%             25  - 35
Free thyroxine index (FTI)    8.0              6 - 11.5
TSH (S)                       3.2 uU/ml       0.7 - 7.0

Notes

TSH changes slowly after T4 is normalized, in both hypo- and hyperthyroid conditions. Up to a month may be required for TSH to come into the normal range. During this time, replacement therapy is monitored using director measurement of free T4, or FTI as a surrogate measurement. Once TSH normalizes, it is the analyte of choice for following patients for adequacy of hormonal replacement.