The active thyroid hormones 3, 5, 3’-triiodothyronine (T3) and thyroxine (T4) are synthesized in the thyroid gland from the hormone precursors 3-monoiodotyrosine (MIT) and 3,5-diiodotyrosine (DIT). These hormones play an essential role in regulating cellular activity, growth, and brain development. However, excessive concentrations of T4 or T3 in the body from either overproduction by the thyroid gland or ingestion of exogenous thyroid hormones can lead to thyrotoxicosis. Symptoms of thyrotoxicosis include excessive thirst and urination, weight loss, increased appetite, restlessness, hyperactivity, elevated heart rate, rapid and/or labored breathing, vomiting, and diarrhea. Continued exposure to excessive hormone levels can cause damage to the heart and result in serious health issues.<br/>In this work we developed, optimized, and validated a method for the detection of Iodide, MIT, DIT, T3, and T4 in wet dog food by liquid chromatography with inductively coupled plasma mass spectrometry detection (LC-ICP-MS) following an enzymatic digestion. A total of fourteen canned dog foods with beef labeled as the first ingredient were analyzed for total iodine by ICP-MS following a basic extraction. Ten of the fourteen canned dog food products were found to have total iodine concentrations above the Association of American Feed Control (AAFCO) maximum of 11 µg/g on a dry mass basis. The concentration of the thyroid hormones and hormone precursors were determined in the ten canned dog foods above the AAFCO maximum by the optimized LC-ICP-MS method. The concentration of the active hormones T3 and T4 in the ten canned dog foods ranged from 0.37 to 5.4 µg/g and 0.12 to 2.1 µg/g, respectively. The average mass balance between the sum of the species measured from the LC-ICP-MS method and the total iodine concentration determined from the basic extraction was 96% with a range of 77-121%.

Analysis of thyroid hormones in commercial dog food by high performance liquid chromatography with inductively coupled plasma mass spectrometry detection

2019 Spring National Meeting

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