IGF1 and cancer: In patients with a clinical suspicion of GHD, the presence of risk factors such as a sellar/suprasellar tumour, hypothalamic–pituitary surgery, hypothalamic/pituitary radiation dose of  ≥ 18 Gy, a single fraction total body irradiation ≥ 10 Gy or fractionated ≥ 12 Gy, younger age at cancer/tumour treatment, longer elapsed time since treatment, or a low IGF-I level may guide the choice of testing and later re-testing (7).