Free 3-methoxy-4-hydroxyphenylglycol (MHPG) in human urine: metabolic routes, biochemical and clinical significance in healthy and obese children.

Conjugated MHPG is an indicator of the adrenergic tonus having clinical use in the follow-up of affective disorders, arterial hypotension, anorexia nervosa and recently of obesity. Little is known about the significance of the unconjugated, free MHPG in various body fluids. Nineteen healthy and 38 obese children were studied as regards the urinary excretion of free MHPG (MHPGF), conjugated MHPG (MHPGC), total MHPG (MHPGT) and also free noradrenaline (NA) valnillyl mandelic acid (VMA) and metanephrines (MN). Part of the obese received a short-term course of drug therapy (diethyl-propion-DEP or thyroid extract) and were subjected to a low-carbohydrate diet containing 800-1000 calories a day. The same urinary determinations were made after diet alone or after diet and drug therapy. MHPGC and MHPGT were significantly higher in the obese children. The level of MHPGF was essentially the same in both groups and did not change significantly following any drug or after diet alone. It was concluded that esterification mechanisms are not involved in the pathological states expressing high or low levels of MHPGC. Suggestion is made that these mechanisms may not be saturated unless huge amounts of MHPG outflow from the brain into CSF.