Thyroid Hormone Withdrawal Occurs When Your Doctor Temporarily Stops Your Thyroid Hormone Medication1
In the treatment and follow up of thyroid cancer, for certain procedures, you need a high level of thyroid stimulating hormone (TSH). A high level of TSH facilitates thyroid cancer treatment and detection of remaining, recurring, or metastatic thyroid cancer.
To obtain a high level of TSH, your doctor may choose to temporarily stop your thyroid hormone medication four to six weeks before treatment with radioactive iodine (RAI), or for diagnostic testing. This process is called thyroid hormone withdrawal (THW).
Normal levels of TSH are between 0.4 to 4 mlU/L. However, when preparing for treatment with radioactive iodine ablation or for diagnostic testing, the TSH needs to be at least as high as 30 mlU/L.2
TSH Levels After Thyroid Hormone Withdrawal (THW)3
It takes 4-6 weeks of stopping thyroid hormone medication for the TSH to go up to the levels required for successful radioactive iodine (RAI) ablation and/or diagnostic testing. (whole-body scan (WBS) or stimulated thyroglobulin (Stim Tg) blood test).
The Impact of Thyroid Hormone Withdrawal
When your doctor asks you to stop your thyroid medication, your hormone level will decrease significantly, and this may lead to signs and symptoms of acute hypothyroidism. Weakness, lethargy, cold intolerance, paleness, dry skin, coarse hair, and constipation can occur with acute hypothyroidism. Other symptoms may include delayed reflexes (such as the knee jerk when the knee is hit with a reflex hammer), brittle nails, increased blood pressure, and a slow heart rate.4
Thyroid Hormone Withdrawal (THW) may result in several weeks of acute hypothyroidism6 Levothyroxine (also commonly known by brand names such as Synthroid, Eltroxin or Levoxyl) is typically stopped for at least four and preferably six weeks prior to the radioactive iodine. Patients who have been on very high doses of levothyroxine for long periods of time may need to stop their medication more than 4-6 weeks prior to their treatment in order for the TSH to increase sufficiently.5
Clinical Studies Show Patients Experiencing Acute Hypothyroidism Experience Greater Levels of Anxiety and Depression as well as Lesser Control of Motor Activities7
Patients experience significantly less depression, anxiety and psychomotor retardation while on their thyroid hormone medication.
“Patients experience a wide spectrum of symptoms during their period of temporary hypothyroidism. Thus, as a precaution, patients who are hypothyroid should avoid making important decisions and driving or operating heavy machinery for one to two weeks before and after the scan or treatment.”4
(MADRS) = Montgomery and Asberg Rating Scale
(HAM-A) = Hamilton Anxiety Scale
(WRS) = Widlo¨cher Retardation Scale