3.0 Introduction to the Analytical Testing Procedures  The Analytical Testing Procedures  for the Endocrine Module involve the measurement of two (2) Markers  of hGH biological activity, namely Insulin -like Growth Factor -I (IGF -I) and N -terminal Pro -peptide of Type III Collagen (P -III-NP), which are naturally present in blood and whose concentrations are increased  following hGH administration 4–11.