Graves' disease following hypothyroidism due to Hashimoto's thyroiditis in a black South African lady: a case report

Effects of block-replace regimen in patients with autoimmune hypothyroidism converted to Graves' disease

PURPOSE

We present two cases of autoimmune hypothyroidism converted to Graves' disease (GD) and their medical management.

METHODS

We tested thyroid function and thyroid antibodies and performed an ophthalmologic examination and neck ultrasound in two patients with autoimmune hypothyroidism converted to GD during a follow-up of several years.

CASE REPORTS

The first case is a 33 year-old woman with hypothyroidism due to Hashimoto's thyroiditis (HT). She developed signs and symptoms of hyperthyroidism after 7 years of treatment with the same dose of levothyroxine (LT4). Even when LT4 therapy was discontinued, she remained thyrotoxic, with mild Graves' ophthalmopathy (GO) and very high thyroid-stimulating hormone receptor antibodies (TRAb > 40 IU/L, reference range: <1.75 IU/L). Antithyroid medication was started on a titration regimen, without achievement of euthyroidism. She was switched to a block and replace regimen, using 20 mg of methimazole (MMI) and 75 mcg of LT4 daily, with normalization of thyroid hormones and improvement of GO without steroids. The second case is a 57 year-old man with a 2-year positive medical history of HT and 6 months of LT4 treatment. He developed hyperthyroidism and moderate-severe GO. Despite stopping LT4 and initiating antithyroid medication in a titration regimen, he did not achieve euthyroidism and had active GO. Pulse glucocorticoid therapy and switching to a block-replace regimen was required to achieve euthyroidism and reduce ocular proptosis and diplopia.

CONCLUSION

Spontaneous autoimmune conversion of hypothyroidism to hyperthyroidism can occur at any time: it is important to promptly identify these cases so as to manage them effectively.

Autoimmune Thyroiditis Shifting from Hashimoto's Thyroiditis to Graves' Disease

In 15-20% of cases, Graves' disease (GD) shifts to Hashimoto's thyroiditis (HT), while the shift from HT to GD is rare. We present a case of a patient in whom HT shifted to GD, along with a literature review. A 50-year-old woman with myxedema was diagnosed with Hashimoto's disease due to hypothyroidism and the presence of antibodies against thyroid peroxidase (TPOAb) and thyroglobulin (TgAb); she also had thyroid stimulating antibodies (TSAb) without any signs of GD. Although thyroid hormone replacement therapy improved her thyroid function, 2 months later, hyperthyroidism appeared and did not improve after discontinuation of the replacement therapy. The patient was diagnosed with GD, which improved with antithyroid agent administration. To date, only 50 cases regarding conversion from HT to GD have been reported. The median age is 44 years (range, 23-82 years), and the median time of conversion is 7 years (range, 0.1-27 years). The male-to-female ratio of HT conversion to GD is 1:9, closer to that of regular GD (1:10) than that of general HT (1:18). All patients received thyroid hormone replacement therapy for hypothyroidism due to HT. Continuous evaluation of TSAb levels is recommended in HT, particularly in cases of TSAb-positive and those under replacement, since it may help predict conversion to GD. Evaluating the clinical characteristics of patients with HT preceding GD is crucial to ensure appropriate treatment and reduce the risk of adverse events.

[The development of Graves' disease after long-term hypothyroidism due to Hashimoto's disease]

The main autoimmune thyroid diseases are Hashimoto's thyroiditis (HT) and Graves' disease (GD). Despite the significant differences in a pathogenesis and a clinical picture between HT and GD, the literature describes the cases of the conversion of one autoimmune disease to another, which, according to one version, is associated with a change in the balance between the levels of a stimulating and blocking antibodies to the thyroid-stimulating hormone receptor. At the same time, there are more frequent observations of the transition of GD to HT, and much less often describe, on the contrary, the development of GD against the background of HT. The article presents a clinical case of the conversion of HT to GD. A detailed algorithm of the conservative management according to the «block-replace» scheme is described, indicating the results of laboratory and instrumental examination. At the time of describing the clinical case, the result of the treatment can be considered successful. The predictors such as a low level of the thyroid-stimulating hormone receptor and thyroid volume before discontinuation of the thyrostatic therapy suggest a low risk of the recrudescence of GD.According to the authors, the phenomenon of the conversion of one autoimmune thyroid disease to another, in addition to the scientific interest, is important for the practitioners, since a timely change in the diagnostic paradigm can significantly change the treatment strategy and the favorably affect the prognosis of disease, preventing the development of complications.

Basedow's disease with associated features of Hashimoto's thyroiditis based on histopathological findings

BACKGROUND

Basedow's disease and Hashimoto's thyroiditis are autoimmune thyroid disorders and usually diagnosed with elevation of serum autoimmune antibodies. Thyrotropin receptor antibodies (TRAb) and/or thyroid-stimulating antibody (TSAb) are usually used for diagnosis of Basedow's disease, and thyroid peroxidase antibodies (TPOAb) and/or thyroglobulin antibodies (TgAb) are for diagnosis of Hashimoto's thyroiditis. However, it is difficult to diagnose a subject as Basedow's disease with associated features of Hashimoto's thyroiditis only with elevation of such autoimmune antibodies.

CASE PRESENTATION

A 44-year-old woman with 5-year history of Basedow's disease underwent a total thyroidectomy. She did not have a goiter. TRAb, TSAb, TPOAg and TgAb were all positive before a total thyroidectomy. In histopathological macroscopic examination, diffuse hyperplasia of the thyroid gland was observed. Furthermore, in histopathological microscopic examination, both characteristics of Basedow's disease and Hashimoto's thyroiditis were observed. After a total thyroidectomy, titers of all thyroid-associated autoimmune antibodies were markedly reduced.

CONCLUSION

Herein, we report a subject with Basedow's disease without a goiter whose TPOAb and TgAb were relatively high at the onset of Basedow's disease. In addition, interestingly, the histopathological findings of this subject showed direct signs of Basedow's disease and Hashimoto's thyroiditis in the same thyroid gland. Considering from such findings, she seemed to have Basedow's disease with associated features of Hashimoto's thyroiditis. In conclusion, we should bear in mind the possibility of Basedow's disease with associated features of Hashimoto's thyroiditis in subjects with Basedow's disease, particularly when TPOAb and TgAb as well as TRAb and TSAb are positive.