Which of the following is the most appropriate initial test to order?

A 35 year old male comes to your office complaining of “feeling cold” for the past 7 months. He notices that he has been using less air conditioning this summer and is always dressed in layers at work. On review of symptoms, he reports a 8 lb weight gain over the past year and says he notices some blood on the toilet paper occasionally from straining to pass his stools on the toilet. Which of the following is the most appropriate initial test to order?

1.Total thriiodothyronine T3 level
2.Total throxine T4 level
3.Thyroid stimulating hormone TSH level
4.Radioiodine scan
5. Fine needle aspiration biopsy

solution

This stem describes a patient with a very classic clinical presentation of hypothyroidism. Characteristic symptoms include weight gain, cold intolerance and constipation, as seen in this patient. Other common manifestations include fatigue, weakness brittle hair and nails, and depression. The best screening test for suspected hypothyroidism is a TSH level. Levels of TSH indicated whether there is primary thyroid disease- and would be elevated if there is a primary thyroid disease (ie Hashimotos thyroiditis) that was the cause of this patient’s symptoms. Alternatively, levels would be low in other types of primary thyroid disease, such as Graves disease, in which there is an overproduction of thyroid hormone and thus symptoms of hyperthyroidism. Although levels of T3 and T4 (options A and B) would be expected to be low in most forms of hypothyroidism, these tests would not help indicate the underlying cause of the disease. Radioiodine scans and fine needle aspiration biopsies (options D and E) are used in the workup of thyroid nodules and masses, and would not be an appropriate first step for this patient.