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Twin Pregnancy, Low TSH, Normal T4 and T3

Last Updated: · Doctors


I am taking care of a 32 year old lady, first pregnancy, at 18 weeks with a twin gestation who comes in with the following thyroid numbers: TSH=0.02 (NV=.30-5.00), Total T4=15.7 (NV=4.5-12.0), Free T4=1.5 (NV=0.71-1.85), free T3=4.1 (NV=2.4-4.2) I repeated the blood work 10 days after the first set of numbers: TSH=0.02, Total T4=15.5, Free T4=1.3, free T3=3.6, Total T3=339 (NV=100-200) She is complaining of occasional palpitations and SOB that sometimes wakes her from sleep. She had been having hyperemesis gravidarum since about the second week of pregnancy and is still having occasional bouts of vomiting. No diarrhea and no heat intolerance. She is gaining weight appropriately. Thyroid stimulating immunoglobulin is pending. My question is: If the TSI comes back within normal limits, could this be HCG-mediated thyrotoxicosis or gestational transient thyrotoxicosis? What would the appropriate treatment for this condition be and would it be reasonable to just repeat bloodwork after a month? I thank you in advance for any advice you could give me.

Patrick Litonjua, MD, Binghamton, NY


Although the TSH is quite low, it is not out of the range seen in the Hyperemesis Syndrome, in this case presumably due to high hCG associated with twins.. The normal free hormone levels are reassuring, as are the total hormone levels which do not exceed 150% of the upper non-pregnant range, and the patient is doing well clinically. I agree withyour plan to wait and re-check levels in a month unless there is a clinical change.

L De Groot, MD