In recent years, many tests of thyroid function have been described using liothyronine (T3) I131 and a variety of adsorptive substances such as red blood cells (RBCs)1 and resins.2-4 More recently, Herbert et al5 have utilized hemoglobin-coated charcoal as the adsorptive material and described a rapid, easily performed liothyronine I 131 uptake test. This test has been modified and simplified using liothyronine I 125, and evaluated in the sera of 238 subjects.
The majority of the patients were seen in the Endocrine Clinic and on the wards of the St. Elizabeth's Hospital. Thyroid status was evaluated by one or more of the following tests: protein-bound iodine (PBI), 24-hour sodium iodide I 131 uptake, and basal metabolic rate (BMR). Patients with nonthyroidal illness were euthyroid but had a wide variety of acute and chronic illness and were taking no medication known to affect thyroxine (T4
Braverman LE, Foster AE, Mead LW. The Charcoal T3 Ratio: An in Vitro Test of Thyroid Function. JAMA. 1967;199(7):469–472. doi:10.1001/jama.1967.03120070081011
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