CME INDIA Case Presentation by Dr Meenakshi Sahapathi, DNB Family Med, Faridabad.
CME INDIA Case Study:
Please comment on dose of thyroxine in patient having twin pregnancy with 9 weeks period of gestation. Was initially on 37.5 mcg of thyroxine. At confirmation of pregnancy 4 weeks back her TSH was 5.530 so thyroxine was increased to 62.5 mcg today’s TFT report is below:
Should dose be decreased to 50 micrograms or again to 37.5?
CME INDIA Discussion
Dr Umesh, Diabetologist, Jaipur: Latest guidelines for pregnancy induced hypothyroidism TSH levels should be less than 2.57.
Dr S S Darriya, Diabetologist, Jaipur: Should be 50. In pregnancy always increases 25% of dose and then escalate according to TSH between 2-3.
Dr Ambrish Bhattacharya, Kolkata: Yes, Keep TSH at or below 2.5.
Dr B K Singh, Aurangabad, Chairman RSSDI, Bihar: Thyroxine dose should be reduced to 50 mcg.
Dr Noni G Singha, Physician, Debrugarh, Assam: Two things can be done here:
- Continue same dose and check after completion of 12 weeks, or
- May reduce the dose of levothyroxine by 12.5 mcg
Dr Subodh Banzal, Endocrinologist, Indore: Agree. Her thyroid function tests are acceptable for pregnancy. By reducing thyronorm dose to 50 mcg daily may bring TSH level to 1 to 2.
Dr Awadhesh K Singh, DM endo., Kolkata: This is a perfectly normal report in first trimester of pregnancy based on total T4 value! Thus, no need to reduce the dose at the moment. Now explain to me why I said this – total T4 value is absolutely normal for pregnancy during first trimester?
Dr Noni G Singha: Agree. This report is normal in certain pregnant lady because of hormonal influence in first trimester. So, the reason for continue same now and recheck after 12 weeks as reassess Secondly, as the above-mentioned case is on levothyroxine supplement so if necessary, adjustment of dose when possible so thought of minimal change in dose is also an option.
Dr Saibal Guha, Diabetologist, Patna: Right, nothing to be done without knowing the free T4 levels, I guess?
Dr Awadhesh K Singh DM endo., Kolkata: Need exact answer! No round and round approach. Not necessary to check FT4. Total T4 is good enough during pregnancy to diagnose treat and monitor – all. Although Free T4 will make the job easier.
Dr Noni G Singha: Increase HCG level (Which peaks around 10-12 weeks of gestation) influences both TSH level and T 4 level after binding with TSH receptor in thyroid gland. Also, TBG level increase in pregnancy stimulates increase production of T4.
Dr V P Youmash, Assistant Professor, KAPV Medical College, Trichy: TSH has structural similarity with beta HCG. So even in normal pregnant individuals, TSH will be low borderline in first trimester due to increased beta HCG. We shouldn’t misinterpret it as suppressed TSH. This may be the reason why the upper limit cut off for TSH in pregnancy is also low 2.5,3 instead of 5.5.
Dr Meenakshi Sahapathi: So, till what level of T4 we should not decrease the dose, this is report after 4 weeks of increase dose and if we wait for another 4 WK’s and see T4 and TSH. Is there no harm?
Dr Prasun Dev, DM, Endo, KIMS Hyderabad:
- Do not reduce the levothyroxine dose. The second reports are normal for pregnancy. Also, as the pregnancy progresses, the dose requirement will go up. So, do not reduce the dose.
- The upper limit of T4 is taken as 1.5 times that of your assay. That is, if the upper limit is 12, during pregnancy it would be 18. Thus, your T4 reports are normal.
CME INDIA Learning Points:
- TSH values vary significantly during the first trimester of pregnancy. Changes encompass two stable periods, the normal TSH one at the very beginning of pregnancy and the low TSH one at weeks 9 to 12. This is followed a partial return of TSH to the initial values. This is important for the evaluation of thyroid function in women during pregnancy and clearly shows that a low TSH can be normal early on in pregnancy and should not be treated.
- Physiological Changes in pregnancy:
- Because of increased metabolic demand of pregnancy, there is increased basal metabolic rate, increased secretion of thyroid hormone due to action of human chorionic gonadotrophin (HCG) and human chorionic thyrotropin (HCT) which share their molecular structure, as well as receptor cross-reactivity with TSH. HCG bears 1/4000th potency to stimulate thyroid activity compared with TSH.
- Transfer of TSH, T3 and T4 across placenta is limited but sufficient for neuroprotection.
- HCG peak at 20 weeks corresponding to nadir of TSH.
- Marked increase of TBG peak at 15 weeks.
- Increased activity of thyroid gland due to direct stimulation by HCG and HCT.
- Decreased free T3 and free T4 levels but within normal range.
- The new recommendations for TSH levels during pregnancy are the following:
- First trimester: less than 2.5 with a range of 0.1-2.5.
- Second trimester: 0.2-3.0.
- Third trimester: 0.3-3.0.
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