ENDEMIC CRETINISM IN THAILAND - A MULTIDISCIPLINARY SURVEY

Endemic cretinism has been classified into neurological and myxedemato us types. Profound mental deficiency, deaf-mutism and cerebral diplegi a are predominantly found in the former. The latter have been describe d as less mentally retarded but with severe growth retardation and myx edematous features. The pathogenesis of different clinical types of en demic cretinism is still unclear. Recently, a unifying hypothesis sugg ested that iodine deficiency, severe enough to cause maternal and feta l hypothyroxinemia, results in neurological defects in all cretins. We conducted the present study in northern Thailand to determine the val idity of this hypothesis in another geographical area. The study consi sted of a multidisciplinary survey on 112 endemic cretins aged 2-66 ye ars in Nan. They were categorized clinically into three types of endem ic cretins, neurological (n=57), myxedematous (n=19) and mixed form (n =36). The subjects were generally short and the majority had severe me ntal retardation (mean intellectual quotient (I.Q.) 30.8 +/- 8.8), psy chomotor defect and profound sensorineural hearing loss. The I.Q. scor e and proportion of cretins with sensorineural hearing loss and psycho motor defect were similar among the three types of cretins. The most f requent neurological abnormalities were spasticity, hyper-reflexia, th e presence of primitive reflexes and gait disturbance. These abnormali ties were distributed equally among the three types of endemic cretins . Delayed skeletal maturation and abnormal epiphysis were also present in all types of cretins. However, myxedematous cretins were shorter ( P<0.01), having more myxedematous features (P<0.05 to P<0.001) and les s sexual maturation (P<0.05). Thyroid volume was lower in cretins with hypothyroidism (P<0.01). In conclusion, our findings support the hypo thesis that neurological features are present in all types of cretins, and are the consequence of maternal and fetal hypothyroxinemia due to severe iodine deficiency. The clinical manifestations of the cretins were subsequently modified by the length and severity of postnatal iod ine deficiency and hypothyroidism.