GH Axis Hypothalamus GHRH (-) Thyroid gland-Anterior pituitary Gonads GH T E Liver IGF-1 Bone epiphysisGH Axis Bone epiphysis Hypothalamus Anterior pituitary SS (-) GHRH (+) GH Liver IGF-1 (-) Gonads T E2 Thyroid gland T3 T4