Here are some quick practical tips for the management of clinical/sub-clinical hypothyroidism during pregnancy. And this post will help you in managing your next patient with these conditions in a better way.
What happens to Thyroxine requirement during pregnancy?
Thyroxine dose requirement increases during pregnancy, by an average of 50% in the first half of pregnancy.
This is due to the accelerated conversion of T4 to reverse T3 (rT3) by placental de-iodinase (type 3).
How shall we monitor such patients?
For the above reason, in women with primary hypothyroidism, monitoring thyroid functions is important during pregnancy.
Plasma TSH level should be measured as soon as pregnancy is confirmed, and monthly thereafter through midgestation, and then at least once near 30 weeks of gestation.
Preferably trimester-specific TSH measurement shall be available.
How shall we adjust the dose of Levothyroxine in pregnant patients?
1. When trimester-specific TSH levels are available, the levothyroxine dose should be increased by 20 to 30%, to maintain plasma TSH levels within the lower half of the trimester-specific range.
2. If trimester-specific TSH levels are unavailable, it is reasonable to target TSH levels <2.5 mIU/L.
3. An alternative approach is to instruct patients to increase their levothyroxine dose by one to two pills per week, as soon as pregnancy is confirmed, and to monitor and adjust the dose of levothyroxine as mentioned before.
After delivery, the pre-pregnancy dose should be resumed.
How shall we pregnant patient with sub-clinical hypothyroidism?
In pregnant patients, known to have subclinical hypothyroidism, if TSH concentration is >2.5 mIU/L, Thyroid PerOxidase antibodies should be checked. If these antibodies are found to be positive, treatment with levothyroxine should be considered.
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