howMed Know Yourself
Case scenario
A 64 year old woman consulted her medical practitioner about her general lassitude
Clinical history
• Included weight gain
• Episodes of constipation
• A blood specimen was taken for thyroid function tests.
| Serum | Result | Unit | Ref Range |
| tT4 | 52 | nmol/L | 60-160 |
| T3 | 1.3 (Normal) | nmol/L | 1.2-2.8 |
| TSH | 28 | mIU/L | 0.2-5.6 |
Impression
- Both the tT4 and fT4 are less than the reference range, but since the patient’s own reference interval is unknown; a biochemical diagnosis cannot be made from these results alone.
- Serum TSH secretion provides a direct indicator in the individual patient of the bioavailability of circulating thyroid hormone
- The TSH concentration in the above case in markedly raised
- The high TSH is therefore diagnostic of primary hypothyroidism
- TSH value greater than twice the upper limit of the reference interval is a biochemical definition of primary hypothyroidism.
