Levothyroxine Dosage Requirement During Pregnancy in Well-Controlled Hypothyroid Women: A Longitudinal Study

Preconceptual thyroid peroxidase antibody positivity in women with recurrent pregnancy losses may contribute to an increased risk for another miscarriage

OBJECTIVE

To investigate preconceptual thyroid peroxidase antibody (TPO-ab) positivity and/or thyroid stimulating hormone (TSH) levels in the upper range of normal as risk factors for recurrent unexplained first-trimester miscarriage.

DESIGN

A post-hoc study of a randomized trial, in which acetylsalicylic acid did not affect the risk of a new miscarriage.

PATIENTS

Women (n = 483) with at least three unexplained recurrent first-trimester miscarriages investigated at a Swedish secondary referral center.

MEASUREMENTS

The levels of TPO-ab and TSH were determined before pregnancy. The occurrence of a new first-trimester miscarriage was analyzed by logistic regression with adjustments when applicable, for age, number of previous miscarriages, obesity and the investigated covariates levels of TPO-ab and TSH.

RESULTS

Including all first trimester miscarriages, odds ratio (OR) according to presence of TPO-ab was 1.60 (95% confidence interval [CI]; 0.99-2.57), after adjustment 1.54 (95% CI; 0.94-2.53). Very early (biochemical) pregnancy losses occurred more often in women with than without preconceptual TPO-ab (6.8% vs. 2.0%), OR 3.51 (95% CI; 1.15-10.71), after adjustment 2.91 (95% CI; 0.91-9.29). There was no association between TSH in the upper range of normal and a new miscarriage, adjusted OR 0.76 (95% CI; 0.32-1.83). A prediction model for a new miscarriage included number of previous miscarriages, woman's age and presence of TPO-ab.

CONCLUSION

In women with at least three recurrent unexplained pregnancy losses, the presence of TPO-ab may contribute to an increased risk of a first-trimester miscarriage, possibly more pronounced in very early pregnancy. TSH levels 2.5-4.0 mU/L do not seem to increase the miscarriage risk.

Levothyroxine dosages during pregnancy among hypothyroid women. An experience from a tertiary care center of Karachi, Pakistan, based on data from Maternal Hypothyroidism on Pregnancy Outcomes Study (MHPO-5)

Objectives

The dosage of levothyroxine (LT4) during pregnancy differs among different ethnic groups worldwide. These differences are due to variations in geographical iodine distribution, autoimmunity, and variations in thyrotropin (TSH) targets for pregnancy. To the best of our knowledge, we report the levothyroxine dosage prescribed during pregnancy in hypothyroid women, for the first time from Pakistan.

Results

Levothyroxine dosage of 280 hypothyroid women during pregnancy were reviewed. The median LT4 dosages prescribed before conception was 85.7 mcg per day which increased by 14.3 mcg per day in the first trimester (P 0.001). A significant difference in dosage was observed between controlled and uncontrolled TSH groups in the first trimester (P 0.05). Lower LT4 dosage was prescribed for subclinical hypothyroid women as compared to overt hypothyroid cases, whereas dosages did not differ according to autoimmune status in the latter part of gestation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13104-022-05984-7.

Thyroxine Replacement for Subfertile Females With Subclinical Hypothyroidism and Autoimmune Thyroiditis: A Systematic Review

The second most prevalent endocrine condition affecting women of reproductive age is thyroid disease. The difference between an increased thyroid-stimulating hormone (TSH) concentration and a normal free thyroxine hormone level is used to identify subclinical hypothyroidism. Thyroid autoantibodies, independent of thyroid hormone levels, are used to diagnose autoimmune thyroid disease (ATD). Thyroxine can help infertile women with these two types of thyroid illnesses have better birth outcomes during fertility treatment. We performed a systematic review using PubMed (Medline) as a major database and some other sources EMBASE, the Cochrane Library, Web of Science, Scopus, and Science Direct. We concentrated on four studies, including 806 patients. Our goal is to investigate the efficacy and risks of levothyroxine therapy in infertile women who are receiving fertility treatments and have subclinical hypothyroidism or adequate thyroid function as well as thyroid autoimmunity (euthyroid autoimmune thyroid disorder). Thyroid activity in hypothyroid women should be tracked at pregnancy confirmation and closely monitored during the pregnancy. Early in pregnancy, the dosage of levothyroxine (LT4) can be raised. To ensure optimum TSH levels during breastfeeding, we recommend that patients who are followed in the primary sector have their LT4 dose increased by their general practitioner before their first referral to an endocrinological outpatient clinic. It's important to pay more attention to and track pregnant women with hypothyroidism, who consider pregnancy, to get the best results. LT4 therapy can help subfertile women with subclinical hypothyroidism who are having in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) since it improves embryo growth, implantation rate, and live birth rate.

Thyroid disorders in subfertility and early pregnancy

Disorders of thyroid function are common in pregnancy and have implications for foetal and maternal health. Thyroid autoimmunity, as evidenced by the presence of elevated levels of anti-thyroid antibodies (anti-TPO and anti-Tg antibodies) is associated with an increased risk of miscarriage, though the mechanism remains poorly understood. There has been considerable focus on the implications and optimal management of pregnant women with thyroid disease, especially those undergoing assisted reproduction. Pregnancy results in significant changes in thyroid physiology and these need to be understood by clinicians involved in the care of pregnant women. Guidelines for the use of thyroxine and target thyroid function tests have been produced by international bodies but it is recognised that these predominantly reflect expert opinion rather than established evidence-based practice. Importantly a number of key clinical trials have been performed to aid understanding, particularly of the consequences of hypothyroidism for mother and baby, and the effectiveness of thyroid hormone use in autoimmune and subclinical hypothyroidism. This review summarises the current knowledge base and guidance for practice relating to thyroid disorders in pregnancy and subfertility.