Function tests

• Assessment of the somatotropic and corticotropic axis, especially in children
• On suspicion of insulinoma in the context of fasting tests or glycogen storage diseases

Induction of hyperglycemia with consecutive increased insulin release and subsequent hypoglycemia.

STH, ACTH, cortisol, glucose (Sodium fluoride plasma)

Per sample collection 2 ml serum, 2 ml sodium fluoride plasma and 1 ml EDTA-plasma (this has to be centrifuged straight away and then frozen)

1. Insertion of an indwelling venous line. First blood collection fasting (0 min), or in case of a fasting test 72 hours after previous morning blood collection

2. Pituitary axis diagnostics: Intramuscular injection of 1 mg glucagon (for adults < 90 kg) or 1,5 mg glucagon (for adults > 90 kg) or 0,03 – 0,1 mg/kg body weight in children
   
   Insulinoma diagnostics: Intravenous injection of 1 mg glucagon

3. Pituitary diagnostics: Further blood collections after 30, 60, 120, 150, 180, 210 and 240 min for ACTH, cortisol, STH
   
   Insulinoma diagnostics: Further blood collections after 10, 20 and 30 min for blood sugar

Pituitary diagnostics:

Adults:

• STH should be > 7,5 µg/l (Assay-dependent) to exclude somatotropic insufficiency
• ACTH should be at least 100 % of the basal value to exclude corticotropic insufficiency
• Cortisol should be at least 50 % of the basal value to exclude corticotropic insufficiency

Children:

• STH should be > 7,5 µg/l (Assay-dependent) to exclude somatotropic insufficiency
• ACTH should increase to at least three times the basal value to exclude corticotropic insufficiency
• Cortisol should increase to > 16 µg/dl to exclude corticotropic insufficiency

Insulinoma diagnostics:

After 72 hours of fasting, blood sugar increase of at least 25 mg/dl after 10, 20 or 30 min confirms the suspicion of an insulinoma.

Glycogen storage disease:

A blood sugar increase < 25 mg/dl after glucagon administration confirms the suspicion of glycogen storage disease, if insulin and C-peptide are suppressed during hypoglycemic phases.