Hypothyroidism in pregnancy

Hypothyroidism in a pregnant woman is defined as TSH levels above the upper limit of pregnancy-specific reference values. Hypothyroidism during pregnancy occurs for the same reasons as outside this period. The most common is autoimmune thyroiditis, or
Hashimoto’s disease
, condition after treatment with radioiodine or removal of the thyroid gland.

Hypothyroidism in pregnancy- symptoms

Among the symptoms of hypothyroidism in pregnancy are:

• feeling of fatigue,
• Drowsiness,
• Nail brittleness,
• hair loss,
• cold feeling,
•  constipation.

Hypothyroidism in pregnancy- research

Hypothyroidism is diagnosed on the basis of clinical symptoms, as well as the result of TSH (elevated) and FT4 (reduced) levels. There is also a subclinical form of hypothyroidism, when TSH is elevated and the FT4 value is normal. It is recommended that a TSH test be performed by every woman in the preconception period or in the first weeks of pregnancy.

According to the 2021 recommendations of the Polish Society of Endocrinology, these are the reference values for the concentration of thyrotropic hormone (TSH), free triiodothyronine (FT3) and free thyroxine (FT4) in each trimester of pregnancy:

In most cases, however, treatment of hypothyroidism in pregnancy is undertaken when TSH levels exceed 2.5 mIU/l in the first trimester and 3 mIU/l in subsequent trimesters.

In addition, once hypothyroidism is diagnosed, it is recommended that a pregnant woman undergo an ultrasound of the thyroid gland. To diagnose the cause, the concentration of antithyroid antibodies in serum is also determined: against thyroperoxidase (anti-TPO) and against thyroglobulin (anti-TG). Increased levels of anti-TPO will be characteristic of Hashimoto’s disease.

Hypothyroidism in pregnancy- treatment

The drug of choice for hypothyroidism is thyroid hormone supplementation in the form of levothyroxine. For women treated in this way before pregnancy, drug doses should be increased for the duration of pregnancy by about 20-30%. In turn, after giving birth, they should be reduced again to the doses taken before pregnancy.

Monitoring the treatment of hypothyroidism in pregnancy involves determining TSH levels every 4 weeks in the first half of pregnancy and at least once around 30. of the week. It is important to take levothyroxine in the morning on an empty stomach, about half an hour before a meal.

Hypothyroidism in pregnancy- complications

Complications of untreated or undiagnosed hypothyroidism during pregnancy include hypertension, anemia, premature separation of the placenta, postpartum hemorrhages and even miscarriage. In addition, intrauterine growth restriction may occur, and the child at birth may have limited cognitive function and a lower IQ. This is due to the fact that for the first 12 weeks of fetal life, the mother’s thyroid is the source of hormones for the baby. If their production is insufficient, the normal development of the child’s central nervous system may be impaired.

Bibliography:

1. Thyroid diseases in pregnancy: recommendations for the management of the Polish Society of Endocrinology, Endocrinologia Polska Volume/Tom 72; Number/Number 5/2021
2. Clinical situations in obstetrics, G.H. Bręborowicz PZWL 2017