A 44-year-old man comes to the clinic due to increasing fatigue, trouble sleeping, and palpitations. He has lost 9 kg (20 lb) over the last year despite eating well. The patient says he is under a lot of pressure at work but cannot think of any other precipitating factors for his insomnia. He has no other medical problems and takes no medications. The patient does not use tobacco, alcohol, or illicit drugs. His mother has a history of a thyroid problem. Blood pressure is 140/80 mm Hg and pulse is 108/min. On physical examination, the thyroid is diffusely enlarged. His serum free thyroxine level is elevated and TSH level is decreased. He is found to have a positive assay for thyrotropin receptor antibodies. If present, which of the following additional findings would be most specific to the underlying cause of this patient's hyperthyroidism?

Question

A 44-year-old man comes to the clinic due to increasing fatigue, trouble sleeping, and palpitations.  He has lost 9 kg (20 lb) over the last year despite eating well.  The patient says he is under a lot of pressure at work but cannot think of any other precipitating factors for his insomnia.  He has no other medical problems and takes no medications.  The patient does not use tobacco, alcohol, or illicit drugs.  His mother has a history of a thyroid problem.  Blood pressure is 140/80 mm Hg and pulse is 108/min.  On physical examination, the thyroid is diffusely enlarged.  His serum free thyroxine level is elevated and TSH level is decreased.  He is found to have a positive assay for thyrotropin receptor antibodies.  If present, which of the following additional findings would be most specific to the underlying cause of this patient's hyperthyroidism?

Quizplus · Accepted Answer

11ec160b_3abe_3db7_9249_f19d8710147a_MD0001_00 This patient has symptomatic hyperthyroidism with elevated serum free thyroxine and suppressed TSH levels. The most common cause of hyperthyroidism is Graves disease, however, hyperthyroidism can also be due to other processes such as toxic adenoma, toxic multinodular goiter, and thyroiditis. This patient's positive serum assay for thyrotropin receptor antibodies (TRAb) confirms the diagnosis of Graves disease. TRAb bind and activate the TSH receptor, causing increased release of thyroid hormone by the thyroid gland, which is responsible for the general symptoms of hyperthyroidism (eg, fatigue, palpitations, weight loss, and insomnia). In addition to the thyroid, the TSH receptor antigen is present on fibroblasts, adipocytes, and other tissues. Thyroid dermopathy is caused by stimulation of fibroblasts by TRAb and activated T-cells, leading to excess production of glycosaminoglycans and adipogenesis. This leads to induration and thickening of the skin over the shins (pretibial myxedema, as shown above). Graves ophthalmopathy occurs in a similar manner, with expansion of the retro-orbital tissues displacing the globe forward (proptosis). Because these processes are directly related to TRAb, they have a high specificity for Graves disease. (Choices A, B, C, and E) Hyperthyroidism also causes a hypermetabolic/hyperadrenergic state that can present with heat intolerance, tremor, lid lag, tachycardia, or atrial fibrillation. In addition, increased bone turnover can lead to osteoporosis and increased fracture risk. However, these findings are not mediated by TRAb and can be seen in hyperthyroidism of any cause (eg, thyroiditis, toxic multinodular goiter). Educational objective: Pretibial myxedema and Graves ophthalmopathy are specific features of Graves disease. They are caused by an autoimmune response directed against the TSH receptor that results in the accumulation of glycosaminoglycans within the affected tissues. __________ References: Thyroid dermopathy and acropachy. (http://www.ncbi.nlm.nih.gov/pubmed/22863396)

A 44-Year-Old Man Comes to the Clinic Due to Increasing