Long-term methimazole therapy in Graves' hyperthyroidism and adverse reactions: a Danish multicenter study

Purpose

In this prospective multicenter study with patients newly diagnosed with Graves' hyperthyroidism (GH), we studied the timing and characteristics of adverse drug reactions in patients treated with anti-thyroid drugs (ATD) for up to 48 months.

Methods

Patients with GH were treated with ATD until remission and hereafter with a low-dose regime to keep the patients in remission. The patients were followed with blood samples and recording of adverse events approximately every second month for the first 2 years and every third month for the following 2 years.

Results

We included 208 patients and the patients were treated for a median of 22 (range: 0.5-49) months. Ten percent of the patients experienced adverse drug reactions and 75% of the cases occurred during the first 6 months. After 24 months, the methimazole dose was lowered to 5 mg/day, and after this time point, no further adverse drug reactions were recorded. Skin reactions were the most prominent reaction, comprising 68% of the registered reactions, and no hepatic and bonemarrow affection was recorded.

Conclusion

With this study, we report the frequency, timing of occurrence, and characteristics of adverse drug reactions when treating GH with the ATD drug methimazole for up to 48 months. Long-term low-dose methimazole treatment can be a cost-effective and straightforward treatment option if adverse drug reactions such as severe hepatic and bone marrow affection are kept in mind.

Hypothyroidism incidence in and around pregnancy: a Danish nationwide study

OBJECTIVE

Immunological changes in and after a pregnancy may influence the onset of autoimmune diseases. An increased incidence of hyperthyroidism has been observed both in early pregnancy and postpartum, but it remains to be studied if the incidence of hypothyroidism varies in a similar way.

DESIGN

Population-based cohort study using Danish nationwide registers.

METHOD

All women who gave birth to a singleton live-born child in Denmark from 1999 to 2008 (n = 403 958) were identified, and data on hospital diagnosis of hypothyroidism and redeemed prescriptions of thyroid hormone were extracted. The overall incidence rate (IR) of hypothyroidism during 1997-2010 and the IR in three-month intervals before, during and after the woman's first pregnancy in the study period were calculated and compared with the IR of hyperthyroidism.

RESULTS

Altogether 5220 women were identified with onset of hypothyroidism from 1997 to 2010 (overall IR 92.3/100 000/year) and 1572 women developed hypothyroidism in the period from 2 years before to 2 years after birth of the first child in the study period. The incidence of hypothyroidism decreased during the pregnancy (incidence rate ratio (IRR) vs overall IR in the rest of the study period: first trimester: 0.89 (95% CI: 0.66-1.19), second trimester: 0.71 (0.52-0.97), third trimester: 0.29 (0.19-0.45)) and increased after birth with the highest level at 4-6 months postpartum (IRR 3.62 (2.85-4.60)).

CONCLUSION

These are the first population-based data on the incidence of hypothyroidism in and around pregnancy. The incidence declined during pregnancy followed by a sharp increase postpartum. Notably, hypothyroidism as opposed to hyperthyroidism showed no early pregnancy increase.