INSULIN TEST

Purpose

To investigate somatotropic function.
To investigate the hypothalamo-pituitary-adrenal system.

Subject preparation

Fasting for 12 hrs and at rest for 30 min (although babies of under one year and hypoglycaemic subjects should be given 200 ml of milk at 5 a.m.).

Product

Regular insulin.

Dose

• Insulin: 0.1 U/kg body weight.

Protocol

• Commence the perfusion of normal saline 30 minutes before the challenge.
• Samples (dry and fluoride tubes) at T-15 and T0.
• IV injection of the correct dose of insulin.
• Samples (dry and fluoride tubes) at time intervals: T+15, T+30, T+45, T+60, T+90 and T+120 min.

Samples

After centrifugation of the samples, freeze the serum at –20°C and store the plasma at +4°C.

Side effects

Close medical supervision because of the risk of HYPOGLYCAEMIA associated with fasting coupled with the insulin: have ready a syringe containing 20 ml 20% glucose solution and a 1 mg vial glucagon.

Contraindications 

• This test is contraindicated in the newly-born and infants.

Assays 

• GH.
• Cortisol.