Methimazole + T3

[aspiringmd1015]

---

Members do not see this ad.

Methimazole is teratogenic, but just saw a quesition explanation saying its main teratogenic effects are in the first trimester, so use PTU in the first trimester in a preg patient, but after the first trimester use methimazole, is this true?
Also, giving synthetic t3, has what effect on TSH and T4? (increased, decreased etc.)

 

[syoung]

giving t3 should decrease TSH, negative feedback

 

[CodeRedDew]

Methimazole is teratogenic, but just saw a quesition explanation saying its main teratogenic effects are in the first trimester, so use PTU in the first trimester in a preg patient, but after the first trimester use methimazole, is this true?
Also, giving synthetic t3, has what effect on TSH and T4? (increased, decreased etc.)

They are both teratogenic; however, methimazole crosses the placenta much more readily than PTU. So you want to avoid methimazole use in the first trimester (which is the critical organogenesis period), but after that it's preferred to ditch PTU and switch over to methimazole for the rest of the pregnancy. This is because there's a much higher risk for hepatotoxicity with PTU compared to methimazole.

 

[aspiringmd1015]

awesome, thanks. one more question, with all the brain stem lesions, anything that effects the Doral column/medial lemniscus system will give you a positive rombergs correct?