Development of Hyperthyroidism Following Primary Hypothyroidism: A Case Report With Changes in Thyroid‐related Antibodies

Abstract

We report a 48-year-old woman who developed hyperthyroidism following primary hypothyroidism. The serum T4 level was initially low and serum TSH level was high with clinical signs of hypothyroidism. The thyroid gland was not enlarged. Therapy with L-T4 was started. Three years later she developed hyperthyroidism; serum free T4 increased to 29.1 pmol/l after cessation of L-T4 therapy. The 123I thyroid uptake was increased with no suppression by exogenous T3. When she was hypothyroid, the activity of thyroid stimulating antibodies (TSAb) in serum measured by cyclic AMP production in cultured porcine thyroid cells were negative at 93.4% (normal less than 140%), while thyroid stimulation-blocking antibodies (TSBAb) determined by inhibition of TSH-induced cyclic AMP increase were positive at 96.1% (normal less than 40%). When hyperthyroidism subsequently occurred, TSBAb became negative (30.9%), while TSBAb became positive (163.3%). The findings indicate that hypothyroidism due to the potent TSBAb activity is not always persistent, but can be changed when various types of thyroid-relating antibodies change in the course of the disease.

Thyrotropin-Blocking Autoantibodies and Thyroid-Stimulating Autoantibodies: Potential Mechanisms Involved in the Pendulum Swinging from Hypothyroidism to Hyperthyroidism or Vice Versa

“…TSAb and hyperthyroidism develop unexpectedly in some patients with hypothyroidism that is caused by TBAb (Table 1) (29)(30)(31)(32)(33). This shift in thyroid function occurs only rarely in a disease that is, in itself, rare.…”

“…The relatively sparse available information for this unusual group of patients is related to age, sex, and ethnicity (5,(29)(30)(31)(32)(33)(36)(37)(38)(47)(48)(49)(50)74). The majority of patients with TBAb/TSAb switches (or the reverse) are women, and they have the same age range as other patients with thyroid autoimmune disease (Table 4).…”

Hyperthyroid Graves' Disease and Primary Hypothyroidism Caused by TSH Receptor Antibodies in Monozygotic Twins: Case Reports.

“…Some patients with Graves' disease who subsequently developed hypothyroidism, and vice versa, have been described [11][12][13][14]. Kasagi et a1.…”

Development of Hypothyroidism with Thyroid Stimulation Blocking Antibody long after Treatment with Antithyroid Drugs in a Patient with Hyperthyroid Graves' Disease: A Case Report.

“…It was therefore of interest that the interval between hyperthyroidism and hypothyroidism in our patient seemed to be quite long when compared with other patients. On the other hand, Takeda et al [17] and Cho et al [ 18] have reported some rare cases which developed hyperthyroidism following primary hypothyroidism.…”