Definition
During pregnancy the need for thyroid hormones increases. Pregnancy hormones stimulate the thyroid gland to produce more. Particularly in the first three months of pregnancy, there is therefore a natural increase in thyroid hormones in the blood.
At the same time, the level of the regulatory hormone TSH decreases. Due to the adjustment processes, which also include a change in thyroid function during pregnancy, there are different limits for the thyroid hormones depending on the stage of pregnancy. If these are exceeded or undercut, this can have a negative effect on the development of the child without treatment. If there is a suspicion that thyroid function is impaired during pregnancy, the thyroid gland values in the blood should be examined in order to initiate treatment in good time if necessary.
Classification of the values
Thyroid levels during pregnancy often cause confusion, as there are many possible constellations with elevated and decreased levels depending on the cause. In addition, different limits apply depending on the stage of pregnancy, i.e. the range in which the values are considered normal. Therefore a compilation of the most important and most frequent constellations is given here.
In the first three months of pregnancy, TSH, the regulatory hormone of the thyroid gland, should be between 0.1 and 2.5. At higher values, hidden hyperthyroidism may be present, which is often not even noticeable otherwise. Only if the thyroid hormones T3 and T4 are also reduced at the same time is there an underactive thyroid leading to symptoms.
Treatment with thyroid hormone tablets should, however, already be carried out if only the TSH is elevated. In the case of hyperthyroidism, the laboratory values are usually altered in exactly the opposite way. A TSH that is too low, i.e. below 0.1 in the first three months or below 0.2 in the second third of pregnancy or below 0.3 in the last phase, indicates an overactive thyroid, which often causes no symptoms at all. Only when T3 and T4 are elevated at the same time, do symptoms usually occur. In this case, too, a conspicuous TSH should be treated with tablets that reduce thyroid hormone production.
