Catecholamine-thyroid hormone interactions: I. Thyroid hormone and platelet MAO activity in psychiatrically disturbed children.

Thyroid hormones are intimately related to mood and behavior, as is vividly evident in the anxiety and agitation of hyperthyroidism and the lethargy of the hypothyroid state. Extremes of activity (augmented or reduced) seen in severe developmental disturbances are often target symptoms for medication, and triidothyronine (T3) has been used in the treatment of childhood psychoses with a beneficial effect in some children (Sherwin, Flack, and Stokes 1958; Campbell et al. 1972). The basis for this therapeutic effect is unknown, but the interaction of thyroid hormones with catecholamines or indoleamines might play a role. Subgroups of autistic children have been characterized by elevated whole blood serotonin (Schain and Freedman 1961) and decreased urinary free catecholamines (Young et al. 1978). Serotonin and the catecholamines are degraded by the intraneuronal enzyme monoamine oxidase (MAO). MAO activity has been reported to have a negative relation with thyroid hormone levels in some animal and human tissues (Skillen, Thienes, and Strain 1961; Levine et al. 1962; Ho-Van-Hap, Babineau, and Berlinguet 1967; Tong and D'lorio 1976; Feldman and Roche 1977), although not all, and may have a significant regulatory function in nerve endings. In order to clarify whether thyroid function is a source of variance in platelet MAO activity, and to better understand the basis for a therapeutic effect of T3 in some disturbed children, we studied the relation between platelet MAO activity and thyroid indices in children with psychiatric disturbances and a control population.