howMed Know Yourself
Case scenario
• A pregnant 26 year old woman (31st week of gestation) presented with complaints of heat intolerance
• Feeling jittery / anxious
• Family history of Grave disease
| Serum | Result | Unit | Ref Range |
| tT4 | 186 | nmol/L | 60-160 |
| T3 | 3.5 | nmol/L | 1.2-2.8 |
| TSH | 2.1 (Normal) | mIU/L | 0.2-5.6 |
Impression
• The high levels of oestrogen during the first two trimesters of pregnancy induce the serum concentration of thyroid binding globulin (TBG) to almost double, increasing the bound fraction of both T4 and T3.
• The rise TBG concentration partly reflects an increase in liver synthesis
• The increased liver synthesis occurs in conditions; of high circulating oestrogen e.g. pregnancy/high oestrogen oral contraceptives.
The most useful test result for assessing thyroid status in above patient in serum TSH
• Which suggests that the circulating free thyroid hormone concentration is normal, and that the patient actually is euthyroid and not hyperthyroid (biochemically).
