Hyperthyroidism of Graves' disease: evidence for only unilateral involvement of the thyroid gland in a 31-year-old female patient

Graves' disease with only unilateral involvement; a case report

INTRODUCTION

Graves' disease characteristically presents with a diffuse goiter secondary to the autoantibodies that target the thyrotropin receptors of the thyroid gland. Few cases have been reported of only one of the two lobes being affected. The cause of this phenomenon is still uncertain. Here we report on another case of unilateral Graves' disease.

CASE PRESENTATION

A 43-year-old female patient presented with a history of weight loss, palpitations and right sided neck swelling for 4 months. Clinical examination showed an enlarged right thyroid lobe. Laboratory investigations yielded evidence of thyrotoxicosis with suppressed thyroid stimulating hormone. In addition, anti-TSH receptor and anti-thyroperoxidase antibodies were positive. Neck Ultrasound showed an enlarged right thyroid lobe with increased vascularization. The isthmus and left lobe were both normal in size. A Tc99m pertechnetate thyroid scan demonstrated enlargement of the right thyroid lobe with diffuse intense uptake, whereas the left lobe was suppressed. A diagnosis of unilateral Graves' disease was made. The thyrotoxicosis was treated and maintained with methimazole.

DISCUSSION

Unilateral Graves' disease is a rare manifestation of Graves' disease, sharing the same autoimmune background and the symptoms of thyrotoxicosis. Enlargement of only one lobe was evident on clinical examination. The distinctive feature was unilateral uptake during thyroid scintigraphy. The exact pathophysiology of this condition has yet to be elucidated. Management options and responses are similar to those of classical Graves' disease.

CONCLUSION

Unilateral uptake during thyroid scintigraphy and/or unilateral lobar goiter in the setting of hyperthyroidism can be the presentation of unilateral Graves' disease.

Unilateral Thyroid Lobe Involvement of Graves Disease

A 30-year-old man presented with 3-year history of Graves disease. He was initially diagnosed after he developed unilateral proptosis and was initiated on methimazole 5 mg, on which he was currently euthyroid. Visible right-sided thyromegaly and trouble swallowing developed 2 months after presentation to our practice. Biochemical evaluation revealed suppressed TSH, normal free T4 and total T3, and elevated thyroid stimulating immunoglobulin with normal thyroid receptor antibody. An ultrasound of the thyroid demonstrated left-sided small nodules with right-sided thyromegaly. A nuclear medicine uptake scan revealed significantly greater uptake in the right thyroid lobe, with overall minimal uptake in the left lobe. The need for definitive therapy that would not exacerbate orbitopathy was discussed, and the patient elected for a right-sided hemithyroidectomy. Postoperative biochemical evaluation demonstrated biochemical euthyroidism despite continued elevation in thyroid stimulating immunoglobulin and newly elevated thyroid receptor antibody while remaining off methimazole. Graves disease can rarely involve a single thyroid lobe. Given the rarity, further investigation is needed to determine the natural course of this form of Graves disease.

Retrospective Study of Tc-99m Thyroid Scan in Patients with Graves' Disease: Is There Significant Difference in Lobar Activity?

PURPOSE

Graves' disease (GD) is the most common cause of hyperthyroidism. It was reported that the right thyroid lobe is generally larger, and it is more likely to be affected by thyroid disorders. The aim of the current study is to verify preferential affection of one of the thyroid lobes and incidence of higher activity of either thyroid lobe in patients with GD through analysis of quantitative data of Tc-99m thyroid scan and possible relation of different thyroid lobar activity to gender, age, and total thyroid uptake (TTU) level.

MATERIALS AND METHODS

Retrospective analysis of quantitative data of Tc-99m thyroid scan in patients with GD was done. Total and lobar thyroid uptake levels were analyzed and correlated with age, gender, and TTU.

RESULTS

GD was reported in 222 patients, representing 76.6% of those with hyperthyroidism, women represent 70.3% of patients. The right thyroid lobe uptake (RLU) figures were significantly higher compared to the left in the whole group as well as in women and in young patients (<40 years). This significance was lost in men and in old patients. Equal lobar uptake was found in 11 patients. 138 patients (62.2%) had higher RLU, while the remaining 73 patients (32.8%) had higher left thyroid lobe uptake, with statistically significant difference. This significant difference was found in women and in young patients and was absent in men and old patients. There is an increase in the incidence of patients with higher RLU in association with an increase in TTU. All women with TTU >30% had higher RLU figures.

CONCLUSION

There is significant preferential thyroid lobar affection in favor of the right thyroid lobe in patients with GD, with significantly higher RLU figures and significantly more incidence of patients with higher right lobar activity. This significance is maintained in women and in young patients and lost in men and old patients. The incidence of higher right thyroid lobe activity also increases in association with increase in TTU. Our results emphasize the value of Tc99m thyroid scan in patients with GD, especially when surgery is the treatment of choice, helping to tailor suitable surgical procedure for each individual patient.

First reported case of unilateral Graves' disease in the left lobe of a bilobar thyroid gland

BACKGROUND

Unilateral Graves' disease is a rare disease variant that can occur in a bilobar thyroid gland. We report the first documented case of unilateral Graves' disease in the left lobe of a bilobar thyroid gland and review the pertinent literature.

PATIENT FINDINGS

A 48-year-old man presented in June 2010 with thyrotoxicosis. I-131 radioisotope uptake was elevated at 33.4%, and scintigraphy revealed that uptake of the radioisotope was uniformly increased in the left lobe of the thyroid gland. Ultrasonography of the thyroid gland revealed a non-nodular, enlarged, and heterogeneous left lobe; Doppler investigation of the lobe showed hypervascularity classically seen in Graves' disease. The right lobe of the thyroid, on the other hand, appeared homogeneous and hypovascular on ultrasonography. Thyroid-stimulating immunoglobulin was significantly elevated at 191% (reference range <140%). Unilateral Graves' disease was the most likely diagnosis.

SUMMARY

As has occasionally been described in the literature, unilateral involvement of the thyroid gland is a rare presentation of Graves' disease. Pre-existing functional or structural differences (either congenital or acquired) between the two lobes may contribute to this rare presentation. To our knowledge, this is the first reported case of unilateral Graves' disease presenting in the left lobe of a bilobar thyroid gland.

CONCLUSION

Although the pathophysiology of unilateral Graves's disease has not been clearly elucidated, clinicians should be aware that Graves' disease can present unilaterally in either lobe of the thyroid gland.

Is sleeping position related to asymmetry in bilateral Graves' ophthalmopathy?

BACKGROUND

In agreement with the systemic nature of Graves' disease, Graves' ophthalmopathy (GO) presents as a symmetric bilateral eye disease in the vast majority of patients. However, asymmetric involvement of both eyes is frequently observed. We hypothesized that sleeping position might be involved in asymmetric GO; when, for example, the preferred sleeping position is on the right side, retrobulbar pressure might be somewhat higher in the right than in the left orbit, resulting in more severe eye changes in the right eye.

METHODS

A prospective study in 75 consecutive untreated patients with GO, in whom eye changes and sleeping position were assessed independent of each other. Criteria for asymmetric eye changes were differences between both eyes in the presence of retrobulbar pain or of > or =1 grade in soft tissue involvement, and/or of > or =2 mm in exophthalmos, and/or > or =8 degrees in elevation. Preferred sleeping position was determined by questionnaire.

RESULTS

All patients had bilateral GO. Eye changes were symmetrical in 50 patients, and asymmetrical in 25 patients based on differences in proptosis and elevation. Sleeping position did not differ between symmetric and asymmetric GO. Preferred sleeping position was on the left side in 23%; on the right side in 31%; and on the back, on the belly, or unknown in 46%. In patients with asymmetric GO, the most affected ("worst") eye was not related to preferred sleeping position on the right or left side.

CONCLUSION

Slight asymmetry of eye changes between both eyes in patients with bilateral GO is not related to preferred sleeping position on either the right or left side.