Monday, March 15, 2010


A 25 year old woman who is 10 weeks pregnant presents with fatigue, nausea, vomiting, and nocturia. These have all had gradual onset over the last few weeks. Her primary care doctor sends off a battery of labs and finds that serum TSH is low, serum total T4 and T3 are both elevated, and free T3 and T4 are at the high end of normal.

Challenge: What is the most likely cause of these findings?

1 comment:

Craig Chen said...


Signs of early pregnancy include amenorrhea, nausea, vomiting, breast tenderness, increased urination, and fatigue. The thyroid function tests here are normal hormonal changes in pregnancy. Estrogen stimulates thyroid binding globulin production and decreases clearance; this leads to increased total T3 and T4. In addition, hCG (produced after fertilization and peaking at 10-12 weeks) has weak thyroid stimulating activity; this can slightly increase free T3 and T4 and decrease TSH.

Source: UpToDate.