Physiological and Pathological Growth Hormone Secretion

Growth hormone (GH) secretion is normally episodic, with discrete bursts of GH super-imposed on a minimal basal level of production. This pattern of GH production yields a dynamic state between a low baseline and intervening peaks, posing a challenge for the clinician attempting to understand the 'true GH status' in a specific patient. This pulsatile pattern is maintained throughout the day, but there are clear differences between different segments of the day, with approximately two-thirds of the total daily secretion produced at night. The dynamic nature of GH production has led many investigators to suggest that when evaluating short stature, parameters of spontaneous GH production be applied rather than the GH response to artificial stimulation. GH secretory patterns in healthy control populations are compared to those in patients with several conditions seen by the pediatric endocrinologist (classical GH deficiency, GH neurosecretory dysfunction, acute lymphoblastic leukemia, hypothyroidism, small for gestational age, Russell-Silver syndrome, constitutional delay of growth and puberty and Fanconi's anemia) and variables used for analysis of these patterns are described. Inferences made from comprehensive evaluations of the GH axis in Fanconi's anemia provide unique insight into general GH pathophysiology.