Resistance to thyroid hormone in a patient with coexisting Graves' disease.

Abstract

BACKGROUND:

Resistance to thyroid hormone (RTH) is a rare disorder in which an abnormality in the binding domain of the thyroid hormone receptor results in end-organ insensitivity to the actions of thyroid hormones. This disorder is sometimes misdiagnosed as Graves' disease due to the presence of a goiter with high Iodine-123 thyroid uptake and high levels of total and free thyroid hormones. Additionally, some patients with RTH may experience palpitations or tachycardia. There is a previous report of a patient with pituitary RTH and concurrent Graves' disease.

SUMMARY:

We describe a patient who was found to have a goiter with signs and symptoms of hyperthyroidism by his primary care physician. Work-up revealed a low thyroid stimulating hormone (TSH), high thyroid-stimulating immunoglobulins, high Iodine-123 thyroid uptake, as well as increased homogenous activity in both thyroid glands on nuclear scan and a suppressed TSH. Diagnosis of Graves' disease was made, and the patient underwent radioactive ablation of the thyroid gland. The patient subsequently developed hypothyroidism and required a much higher dose of levothyroxine than his weight-based estimate of a full replacement dose to maintain euthyroidism. On 325 micog of daily levothyroxine the patient was clinically euthyroid and had a normal TSH although his levels of T3 and T4 were high. Work-up revealed a mutation in the thyroid hormone beta-receptor gene, consistent with diagnosis of RTH.

CONCLUSIONS:

RTH is often misdiagnosed as Graves' disease. However, these disorders can coexist, and the concurrent presence of both disorders in a patient can present diagnostic challenges. A previous report of a patient with Graves' disease associated with RTH was published before gene sequencing could be used to confirm diagnosis of RTH. We present a patient with Graves' disease and concurrent RTH that was confirmed by gene sequencing, showing a mutation in the thyroid hormone receptor beta gene.

• Authors: Tharsan Sivakumar, Sushela Chaidarun
• Journal: Thyroid : official journal of the American Thyroid Association (Thyroid) Vol. 20 Issue 2 Pg. 213-6 (Feb 2010) ISSN: 1557-9077 [Electronic] United States
• PMID: 20151830 (Publication Type: Journal Article)

Chemical References

• Thyroid Hormone Receptors beta
• Thyroxine

Topics

• Graves Disease (complications)
• Humans
• Hypothyroidism (genetics)
• Male
• Middle Aged
• Thyroid Hormone Receptors beta (genetics)
• Thyroid Hormone Resistance Syndrome (complications, diagnosis, genetics)
• Thyroxine (therapeutic use)