AUTHOR=Yun Taesik , Na Yejin , Lee Dohee , Koo Yoonhoi , Chae Yeon , Nam Hyeyeon , Kang Byeong-Teck , Yang Mhan-Pyo , Kim Hakhyun 

TITLE=Case Report: Technetium-99m Pertechnetate Scintigraphy Findings in a Dog With Iodine Deficiency-Induced Goitrous Hypothyroidism

JOURNAL=Frontiers in Veterinary Science

VOLUME=Volume 9 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/veterinary-science/articles/10.3389/fvets.2022.922456

DOI=10.3389/fvets.2022.922456

ISSN=2297-1769

ABSTRACT=There is only one previous report of canine goitrous hypothyroidism caused by iodine deficiency from 1986. The present case report describes the novel diagnostic methods and long-term outcomes of a dog diagnosed with goitrous hypothyroidism caused by iodine deficiency. A 4-year-old neutered, female Pomeranian dog presented with a cervical mass, lethargy, and inactivity. The dog had a history of eating home-cooked diets sold by a private seller for 1 year. The physical examination and ultrasonography showed two bilaterally symmetric masses in the mid-cervical area (left, 1.8×1.4 cm; right, 2.3×1.8 cm), and they were suspected to be the thyroid glands. To identify the function of the thyroid gland, the basal concentrations of thyroid hormones (total T4 [tT4] and thyroid-stimulating hormone [TSH]) were measured and a TSH stimulation test was performed: baseline tT4, 0.5 µg/dL (reference interval, 1–4 µg/dL), baseline TSH, 0.81 µg/dL (reference interval, 0.05–0.42 ng/dL), and post-tT4, 1 µg/dL (6 hours after the injection of TSH). The values indicated primary hypothyroidism. The urinary iodine concentration was 302 µg/L, which was markedly lower than that of normal dogs (1289 µg/L). Thyroid scintigraphy with technetium-99m pertechnetate was also performed to quantify the activity of the thyroid gland, and the thyroid-to-salivary ratio was 3.35. Based on the results of these examinations and patient history, the dog was diagnosed with diet-induced (iodine deficiency) goitrous hypothyroidism. The dog was treated with iodine (62.5 µg/day). At 31 days after treatment, clinical signs and thyroid hormones were normalized (tT4, 1.3 µg/dL; TSH, 0.24 µg/dL). One year after treatment, the dog was well with normal concentrations of thyroid hormones (tT4, 1.8 µg/dL; TSH, 0.27 µg/dL) and a partially reduced goiter (left, 1.6×1.1 cm; right, 1.2×0.9 cm). This is the first case to describe novel diagnostic methods and long-term outcomes of a dog diagnosed with goitrous hypothyroidism caused by iodine deficiency.