Treating thyrotoxicosis in pregnant or potentially pregnant women

Essentiality, relevance, and efficacy of adjuvant/combinational therapy in the management of thyroid dysfunctions

Thyroid dysfunction is the most prevalent endocrine disorder worldwide having an epidemiology of 11% in Indians, 4.6% in the United Kingdom, and 2% in the United States of America among the overall population. The common thyroid disorders include hypothyroidism, hyperthyroidism, Hashimoto's thyroiditis, and thyroid cancer. This review briefly elaborates the molecular regulation and mechanism of thyroid hormone, and its associated thyroid disorders. The thyroid hormones regulate critical biochemical functions in brain development and function. Hypothyroidism is mainly associated with dysregulation of cytokines, increased ROS production, and altered signal transduction in major regions of the brain. In addition, it is associated with reduced antioxidant capacity and increased oxidative stress in humans. Though 70% of thyroid disorders are caused by heredity, environmental factors have a significant influence in developing autoimmune thyroid disorders in people who are predisposed to them. This drives us to understand the relationship between environmental factors and thyroid dysregulated disorders. The treatment option for the thyroid disorder includes antithyroid medications, receiving radioactive iodine therapy, or surgery at a critical stage. However, antithyroid drugs are not typically used long-term in thyroid disease due to the high recurrence rate. Adjuvant treatment of antioxidants can produce better outcomes with anti-thyroid drug treatment. Thus, Adjuvant therapy has been proven as an effective strategy for managing thyroid dysfunction, herbal remedies can be used to treat thyroid dysfunction in the future, which in turn can reduce the prevalence of thyroid disorders.

Radioiodine I-131 for the therapy of graves' disease

Graves' disease is a common cause of hyperthyroidism. Treatment options for Graves' disease include antithyroid medication, surgery or radioactive iodine (I-31) or RAI. This review will focus on the approach to RAI therapy; discussing dose selection, patient preparation, and consideration before and after administering RAI, examining aspects of pre-treatment with antithyroid medication as well as discussing possible adverse events including hypothyroidism and possible worsening of thyroid-associated opthalmopathy. Follow-up is lifelong with the aim of ensuring the patient remains euthyroid or on replacement therapy if there is evidence of hypothyroidism. While there are controversies in treatment of thyrotoxicosis with RAI, with appropriate patient selection and regular follow-up, radioiodine is a safe and effective modality in achieving high cure rates.

Case Studies

Ms A was a 28 year old woman in her second pregnancy (she had one previous termination of pregnancy) who booked-in at 19 weeks’ gestation. She was known to have sickle cell disease (specifically sickle cell anaemia [HbSS]), and her last crisis had occurred 3 years before this pregnancy.

Outcomes of pregnancy complicated by thyroid disease

AIMS

To perform a case note review of pregnancies complicated by thyroid dysfunction to determine management and therapeutic intervention in relation to pregnancy outcome.

METHODS

A retrospective case note analysis of 81 ongoing pregnancies in 70 pregnant women with a history of thyroid dysfunction over a period of 5 years at the Glasgow Royal Maternity Hospital (GRMH), Glasgow, Scotland, United Kingdom. The results of thyroid function tests and whether a change in treatment was instituted were recorded. Thyroid function was assessed by standard laboratory reference ranges for free thyroxine (FT4) and thyroid stimulating hormone (TSH) in all trimesters. Other parameters were also noted.

RESULTS

Medication levels needed to be increased in the hypothyroid group (45%), and decreased (38%) in the hyperthyroid group.

CONCLUSION

Pregnancy outcome was good in majority of cases given appropriate replacement therapy for stated reference values.

Obstetric complications due to autoantibodies

Autoimmune diseases are most common and most active in young women; it is therefore not uncommon for obstetricians and physicians to encounter pregnant women with these conditions, and knowledge of the potential maternal, foetal and neonatal complications is essential for good clinical management. The most common maternal autoimmune endocrine conditions in pregnancy are insulin-dependent diabetes mellitus and thyroid disease. Other relatively common non-endocrine autoimmune conditions include systemic lupus erythematosus and anti-phospholipid syndrome. Much rarer autoimmune conditions include autoimmune thrombocytopenia, rheumatoid arthritis, myasthenia gravis and Addison's disease. In this chapter, we discuss autoimmune endocrine conditions and briefly mention some non-endocrine conditions of particular importance.

Postpartum recurrence of Graves' hyperthyroidism can be prevented by the continuation of antithyroid drugs during pregnancy

OBJECTIVE

Previous studies recommend the discontinuation of antithyroid drug (ATD) therapy during pregnancy in women with well-controlled Graves' hyperthyroidism (GH). In this study, we investigated whether this termination of ATD therapy during pregnancy is beneficial in terms of postpartum GH recurrence.

DESIGN

A nonrandomized, retrospective study.

PATIENTS

Sixty-five pregnant GH patients treated with maintenance doses of ATDs were assigned into two groups: ATD therapy was discontinued before delivery in Group 1, but continued during pregnancy and after delivery in Group 2.

MEASUREMENTS

The prevalence of postpartum recurrence or exacerbation of GH within 1 year after delivery was examined. Serum T4, T3 TSH, and TSH receptor antibody levels were measured.

RESULTS

In Group 1, 70.8% (17/24) of patients suffered a recurrence of GH within 1 year after delivery. In contrast, a postpartum exacerbation of GH was observed in only 29% (12/41) of patients in Group 2 (P < 0.01). Both exacerbations and recurrences of GH appeared primarily within 4-6 months after delivery. Apparent neonatal hypothyroidism and malformations were not observed in the offspring of either group.

CONCLUSION

Continuing antithyroid drug therapy throughout pregnancy prevents postpartum recurrence of Graves' hyperthyroidism without resulting in neonatal hypothyroidism or malformations.

Drugs in pregnancy. Drugs to avoid

Drugs given in pregnancy can adversely affect the fetus in many ways. Anxiety about birth defects is a major parental concern during pregnancy. Doctors, midwives and their patients often seek information about the potential teratogenicity of drugs that are taken by, or prescribed for, the pregnant woman. Because no drug is entirely without side-effects, great caution should be taken when prescribing in pregnancy. The development of knowledge in understanding the use of drugs during pregnancy has been in stalemate in comparison to other areas of therapeutics, due mainly to difficulties in testing new products in pregnant women and lack of good quality research. In this chapter, we review current knowledge of the epidemiology of drug use among pregnant women, drug metabolism in pregnancy, adverse fetal and neonatal effects of drugs and specific effects of drugs that are relatively or absolutely contraindicated in pregnancy.

Drug therapy for hyperthyroidism in pregnancy: safety issues for mother and fetus

Hyperthyroidism (thyrotoxicosis) in pregnancy and the child bearing years is usually attributable to Graves' disease. This is an autoimmune condition in which thyroid-stimulating immunoglobulins (TSI) cause hyperthyroidism. As a rule, pregnancy complicates the management of hyperthyroidism, rather than vice versa. However, patients who remain thyrotoxic during pregnancy are at increased risk of maternal and fetal complications, particularly miscarriage and stillbirth. Therefore, bodyweight loss, eye signs and a bruit over the thyroid gland in a pregnant woman warrant thyroid investigation. Investigations should include measurement of serum free thyroid hormone levels [free thyroxine (T4) and free triiodothyronine (T3)] rather than total T4 and T3 levels, because total T4 and T3 levels may be raised in euthyroid pregnancies due to the presence of increased levels of thyroxine binding globulin (TBG). By 20 weeks' gestational age, the fetal thyroid is fully responsive to TSI and to antithyroid drugs. Maternal T4 and T3 and thyrotropin pass across the placenta in small and decreasing amounts as gestation progresses, but thyrotropin releasing hormone, TSI, antithyroid drugs, iodides and beta-blockers are readily transferred to the fetus from the mother. Hyperthyroidism is usually treated throughout pregnancy with an antithyroid drug, preferably propylthiouracil. The smallest dose which controls the disease is given with careful monitoring of free T4 and T3 levels to minimise the risk of fetal hypothyroidism and goitre. Bilateral subtotal thyroidectomy may be an option for a small number of patients with hyperthyroidism in pregnancy.

Thyroid disease in relation to pregnancy: a decade of change

Inspection of the references cited in this review indicates that much work has occurred in the area of thyroid and pregnancy during the last decade. Significant advances in our understanding of the immunology of pregnancy and the effect of thyroid disease on this process have taken place. The role of hCG in the physiology of pregnancy and its relevance to thyroid function has been an emerging theme. There is still no clear explanation for the association between thyroid antibodies and infertility or miscarriage. During the last decade a general concensus has developed in relation to the management of hyperthyroidism in pregnancy although there are still variations in antithyroid drug use at this time. The aetiological classification of congenital hyper- and hypothyroidism utilizing new technologies has opened up a new perspective on these disorders. Attention has been drawn to the importance of treating maternal hypothyroidism with adequate thyroid replacement therapy and to the possibility of impaired child neuropsychological development consequent on low maternal thyroid hormone concentration in early gestation in non iodine deficient areas. Significant advances have been made during the last decade in the description of the clinical features and in our understanding of the pathogenesis of postpartum thyroid disease. The importance of long-term follow up of selected patient groups has also been emphasized.