Monday, March 21, 2016

But Why?

A 30 year old previously healthy woman who is 11 weeks pregnant complains of heat intolerance, sweating, and anxiety. On examination, you note tachycardia and hand tremor. Her pregnancy has been notable for morning sickness and a slower weight gain than expected. A brilliant diagnostician, you send off thyroid function tests. Serum free T4 and T3 are slightly elevated. TSH is reduced.

The next time you see the patient, before you start any therapy, she is 15 weeks gestation. She says her symptoms have completely disappeared.

Challenge: How do you explain this?

Image is shown under Creative Commons Attribution Share-Alike License, from Wikipedia.


Anonymous said...

she has HcG-induced hyperthyroidism? :D it's disappeared by 15 weeks since that's when the placenta (largely) becomes self-sufficient in producing its own progesterone to maintain the pregnancy, and the corpus luteum is no longer needed.

RaH said...

So this women presents with Hyperthyroidism during pregnancy...
now the question is why did it appear and why did it disappear.
Symptoms appeared shortly before the 11th week, this is around the HCG-peak, and disappeared around the 15th week HCG is low again.
There is this control loop between pregnancy hormones and the pituitary axes. HCG due to its similar structure to TSH would cause a decreased serum TSH and elevated T3 and T4.

This is what i recall from my GYN exams.

Craig Chen said...

yes! nice review of the pathology - good job!
But Why?

During normal pregnancy, serum human chorionic gonadotropin (hCG) peaks at 10-12 weeks gestation. There is homology between the beta subunits of hCG and TSH; thus, it can cause a gestational transient thyrotoxicosis which resolves when hCG production declines.

Source: UpToDate.