The nutritional supplement biotin (vitamin H or vitamin B7), which is often taken for skin, hair, and nail growth disorders, can distort measured values. In many of the laboratory methods used, the biotin competes with the test substances used. As a result, it can lead to falsely high and falsely low TSH values. At high doses of biotin (for example, 10 mg), there should be at least a 3-day pause (and ideally a pause of 1 week) before measuring TSH.
Hasty prescriptions
“Sometimes, because of the assumption that every high TSH value is due to sickness-related hypothyroidism, thyroid hormones can be prescribed too quickly,” said Dr. Feldkamp. This is also true for patients with thyroid nodules due to iodine deficiency, who are often still treated with thyroid hormones.
“These days, because we are generally an iodine-deficient nation, iodine would potentially be given in combination with thyroid hormones but not with thyroid hormones alone. There are lots of patients who have been taking thyroid hormones for 30 or 40 years due to thyroid nodules. That should definitely be reviewed,” said Dr. Feldkamp.
When to treat?
Dr. Feldkamp does not believe that standard determination of the TSH value is sensible and advises that clinicians examine patients with newly occurring symptoms, such as excess weight, impaired weight regulation despite reduced appetite, depression, or a high need for sleep.
If there are symptoms, the thyroid function must be clarified further. “This includes determination of free thyroid hormones T3 and T4; detection of antibodies against autologous thyroid tissue such as TPO-Ab [antibody against thyroid peroxidase], TG-Ab [antibody against thyroglobulin], and TRAb [antibody against TSH receptor]; and ultrasound examination of the metabolic organ,” said Dr. Feldkamp. Autoimmune-related hypothyroidism (Hashimoto’s thyroiditis) is the most common cause of an overly high TSH level.
Treatment should take place in the following situations:
- In young patients with TSH values greater than 10 mU/L;
- In young (< 65 years) symptomatic patients with TSH values of 4 to less than 10 mU/L;
- With elevated TSH values that result from thyroid surgery or radioactive iodine therapy;
- In patients with a diffuse enlarged or severely nodular thyroid gland
- In pregnant women with elevated TSH values.
This article was translated from Medscape’s German Edition and a version appeared on Medscape.com.