Hashimoto’s thyroiditis is the most common thyroiditis and the main cause of hypothyroidism. But elevated TSH levels can also be due to various other factors. Therefore, repeated measurements and differential assessment are advised before thyroxine administration is prescribed.
The hormone thyroxine (T4) produced by the thyroid gland is the most important thyroid hormone and is vital for numerous metabolic processes. The rate of T4 secretion is controlled by TSH (thyrotropin) secreted from the pituitary gland as part of the thyrotropic regulatory circuit. An elevated TSH level may mean that the thyroid gland is not producing enough thyroid hormone. But there are other explanations, such as seasonal variations [1]. According to a recent study, TSH levels tend to be higher in winter than in summer [2]. Acute sleep deprivation, physical exertion, infections, puberty, older age, or obesity should also be considered as underlying factors. If patients are otherwise symptom-free, the German Society for Endocrinology (DGE) recommends that a new TSH determination be performed before therapeutic administration of the thyroid hormone thyroxine [1]. And at least 2, better 6 months after the first test. In about half of the cases, a normal value is then measured, according to the DGE.
Are there antibodies against the patient’s own thyroid tissue?
“Formally, hypothyroidism is present when the TSH value is above the upper limit range of 4.2 mU/l,” explained Prof. Joachim Feldkamp, MD, Bielefeld Mitte Hospital [1]. “But individual measurements should be taken with great caution. They almost never justify a therapy decision,” says Prof. Feldkamp. Are there complaints such as overweight, disturbed weight regulation. Depression and high sleep need to be further clarified thyroid function. “These include determination of free thyroid hormones T3 and T4, detection of antibodies to the patient’s own thyroid tissue such as TPO-AK, TG-AK, and TRAK, and ultrasonography of the metabolic organ” [1]. If these tests are positive, the most common cause of high TSH levels is autoimmune hypothyroidism (Hashimoto’s syndrome). The therapy of choice is hormone replacement with L-thyroxine (Fig. 1) [3].
Literature:
- “Thyroid: When TSH is elevated: caution in diagnosis – context matters,” DGE, Aug. 29, 2023.
- Yamada S, et al: J Endocr Soc. 2022 Apr 6; 6(6): bvac054.
- “Elevated TSH in family practice,” S2k guideline, 2023, abridged version, AWMF registry no. 053-046.
HAUSARZT PRAXIS 2023; 18(9): 23
