| Material | serum or heparin plasma 0.5 ml resp. 0.4 ml (small mammals) |
| Method | CLIA |
| Duration | 1 day |
| Remark | - Canine: Most frequently used to diagnose hypothyroidism. Caution: A low T4 serum concentration is not necessarily associated with hypothyroidism. TSH is required for further assessment. In addition, rT3 can help differentiate non-thyroidal causes.
- Monitoring canine hypothyroidism: Blood sampling 4-6 hours after thyroxine administration. Monitor every 2-4 weeks until adequate control of hypothyroidism is achieved. Then every 3-6 months. Aim for a T4 concentration in the middle to upper reference range.
- Feline: Most frequently used to diagnose hyperthyroidism. Increased T4 serum concentrations indicate hyperthyroidism.
- Monitoring feline hyperthyroidism: Monitor every 2-4 weeks until euthyroidism is achieved. Then every 3-6 months. Aim for middle reference range. Very low T4 levels should be avoided.
- Birds and reptiles: Values are physiologically often very low below the detection limit of the test system used); in this case, determination of T4 (bird, reptil) (service 1089) is recommended.
- Horse: If (very rarely occurring) hypothyroidism is suspected, determination of T4 and T3 with a subsequent TRH stimulation test is recommended.
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