Tc-99m-tetrofosmin thyroid scan in patients with low I-131 thyroid uptake.
 

Low 24-hour thyroid uptake of I-131 (I-131 uptake) is a common finding that influences evaluation of the thyroid gland. METHODS: We studied 20 female patients aged 16-82 years with low I-131 uptake. The following causes of reduced I-131 uptake were defined as (A) six cases with subacute thyroiditis, (B) seven cases with T4 suppression therapy, and (C) seven cases with iodinated pharmaceuticals use. Thirty-minute Tc-99m tetrofosmin thyroid scan was performed within 24 hours of the I-131 thyroid study. RESULTS: The results were correlated with neck ultrasound, serum TSH and biopsy histopathological findings. Tc-99m tetrofosmin thyroid scans revealed 10 normal thyroids, five diffuse goiters, four multinodular goitres, and one solitary thyroid nodule. CONCLUSIONS: Our results suggest that Tc-99m tetrofosmin thyroid scans may provide additional information to diagnose thyroid pathology in patients with low 24-hour I-131 uptake. COMMENT: there are several factors that may suppress uptake of radioiodine by the thyroid, including diet, inflammation, and medications. Tc-99m Tetrofosmin is useful because it overcomes these complicating factors. Thus, it is inappropriate to assume that all patients needing a thyroid scan should be taken off of their thyroid hormone replacement therapy, because Tc-99m tetrofosmin can be used in these patients. Also, Tc-99m pertechnetate may be useful when the patient remains on thyroid hormone therapy, because an autonomously functioning thyroid nodule is TSH independent.


Endocr Res. 2002 Aug;28(3):231-8.

Tc-99m-tetrofosmin thyroid scan in patients with low I-131 thyroid uptake.

Wang TY, Wu HS, Lin CC, Lee CC, Kao CH.

Division of Endocrinology and Metabolism, China Medical College Hospital, Taichung, Taiwan.

http://www.ncbi.nlm.nih.gov/entrez/...t_uids=12489572