Thyroxine - T4 (Serum) During Pregnancy

Laboratory Tests

Obie Editorial Team

What is Total Thyroxine?
The total thyroxine test is typically ordered to measure thyroid function. Patients with symptoms of hyperactive or hypoactive thyroid may present with abnormal total thyroxine levels. Goiter and infertility testing may also include total thyroxine blood tests.

When a total thyroxine blood test is ordered, the ordering physician will also order a free thyroxine and thyroid stimulating hormone test along with other blood tests. If a thyroid stimulating hormone (TSH) test was run earlier and an abnormal result was measured, the doctor may order a total thyroxine and free thyroxine test as a follow-up to the TSH test.

Normal Value Range
  • Negative Pregnancy Adult: 5.4 to 11.7 µg/dL or 69 to 151 nmol/L
  • Pregnancy Trimester One: 6.5 to 10.1 µg/dL or 84 to 130 nmol/L
  • Pregnancy Trimester Two: 7.5 to 10.3 µg/dL or 97 to 133 nmol/L
  • Pregnancy Trimester Three: 6.3 to 9.7 µg/dL or 81 to 125 nmol/L

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