PROTOCOL

1. Take 5ml of clotted or heparinised blood.
1. Inject 1mg (1000 mg) of thyrotropin releasing hormone (TRH) slowly i/v over one minute.
1. Take two further samples of 5ml clotted or heparinised blood at 15 minutes and 60 minutes post TRH injection.
1. If possible separate the serum or plasma before despatch to the laboratory and label the tubes carefully. 

In horses with pituitary adenoma, significant increases in cortisol concentrations are seen at 15 minutes (mean 90% increase) and 60 minutes (mean 58% increase) post TRH stimulation.

In normal horses, cortisol concentrations may be elevated at 15 minutes (mean 17% increase) but return to baseline values at 60 minutes (mean 5% decrease) post TRH stimulation (Beech and Garcia, 1985).

TRH SUPPLY.

TRH is available on prescription as Protirelin (Roche) (licenced for use in humans only; 0.2mg/vial).
 

Test Code	Test Name and Description	Sample
TRHE	TRH Stimulation Test Equine	3 x Serum/Heparin Plasma

REFERENCES

Beech, J and Garcia, M (1985) Hormonal response to thyrotropin - releasing hormone in healthy horses and in horses with pituitary adenoma. Am.J.Vet.Res. 46(9) p 1941 - 1943.

Eustace, R (1991) Equine pituitary neoplasia. In Practice 13(4) p 147 - 148.