Version July 2025
ATA: American Thyroid Association; LLN: lower limit of normal reference range; rhTSH: recombinant human TSH; TSH: thyroid-stimulating hormone.
* Low-risk patients and most intermediate-risk patients are unlikely to need radioiodine scanning or ablation. Risk is defined using the ATA risk stratification system. This system stratifies patients primarily based on clinicopathologic findings.
¶ Radioiodine uptake by thyroid tissue is stimulated by TSH. There are 2 methods for increasing TSH: administration of rhTSH (thyrotropin alfa) or thyroid hormone withdrawal. We routinely use rhTSH for radioiodine scanning and radioiodine therapy even in patients with gross residual disease or distant metastasis. However, rhTSH does not have regulatory approval for radioiodine therapy in patients with distant metastases.
Δ Goal TSH is based upon ATA risk of disease recurrence.
◊ Avoid thyroid hormone withdrawal in patients with relative contraindications to hypothyroidism (eg, depression, heart failure, severe sleep apnea).
§ After thyroidectomy, it takes approximately 3 to 4 weeks for the serum thyroxine concentration to decline sufficiently to allow the TSH to rise to >25 to 30 mU/L (goal TSH to ensure adequate radioiodine uptake).
¥ Advise a low-iodine diet for 7 to 10 days prior to planned radioiodine administration.
‡ Lower doses (eg, 10 mcg, 2 or 3 times per day) or rhTSH stimulation should be used in older patients and those with ischemic heart disease. After cessation of liothyronine, the serum TSH concentration should rise to 25 to 30 mU/L within 1 to 2 weeks. Thus, the interval during which the patient receives no thyroid hormone is shortened.
† Levothyroxine is continued during radioiodine administration.