Thyroid hormone-induced reduction of urinary 5-hydroxyindole acetic acid (5 HIAA) in obese children. Comparison with hypothyroid patients of similar age having either pituitary dwarfism or congenital myxedema.

Urinary excretion of monoamine metabolites (noradrenaline-NA, adrenaline-A, 3-methoxy-4-hydroxyphenyl glycol-MHPG, homovanillic acid-HVA, 5-hydroxyindole acetic acid-5 HIAA) was studied in four groups of children as follows: Group I consisting of obese children subjected to caloric restriction and to a short term course of thyroid extract in "low" dosage (1-2 mg/kg bwt), Group II consisting of obese children subjected to diet alone, Group III consisting of children myxedema and subjected to a short term course of thyroid extract given in the "high" dosage (3-5 mg/kg bwt) and Group IV consisting of GH deficient short children having (many of them) thyrotropin deficiency and subjected to a short term course of thyroid extract in "very high" dosage (5-10 mg/bwt). In obese, calorie-restricted children, the previously low mean level of 5 HIAA excretion was further lowered by thyroid extract. In obese children subjected to calorie restriction alone no urinary abnormality was noted. The congenitally hypothyroid patients had low levels of basal 5 HIAA when compared to controls. The degrees of 5-hydroxy tryptamine (5 HT) deficiency in Group III was similar to the obese groups. The thyroid extract course did not influence, at least in short term administration, the low 5 HIAA levels in group III. In GH deficient, short children (group IV) thyroid extract had no significant effect on urinary pattern of monoamine metabolites. A central 5 HT deficiency may tentatively explain the mood disturbances and possibly the other psychic disorders in both the obese and myxedematous patients. The different effects of thyroid extract on 5 HIAA may also witness the differences in the food intake behaviour in these two conditions.