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Motor and cognitive development in children with congenital hypothyroidism
EDITORIAL CORRESPONDENCE
Motor and cognitive development in children with congenital hypothyroidism To the Editor: We appreciate the difficulty in conducting a long-term follow-up study of children with congenital hypothyroidism such as the one reported by Kooistra et al. (J PEDIA'rR 1994;124:903-9). The article concludes that hypothyroid children with low screening thyroxine (T4) concentrations (<50 nmol/L), despite early treatment, are likely to have borderline intelligence and motor problems. If taken at face value, this implies that families with athyreotie children should be resigned to a less-than-optimal outcome. This is also disheartening news for the physician, especially if he or she is convinced that nothing can be done to prevent the cognitive and motor problems. However, before such a pessimistic (and self-defeating) attitude is allowed to overtake us, it is crucial to ask whether the children in the study were treated adequately. A careful reading of the article shows that no data confirm the authors' statement of adequate T4 replacement therapy. With the exception of the screening mean T4 values, we can find no figures relative to T4 and thyrotropin concentrations during the first year of life, when inadequate levels of circulating T4 correlate significantly with poor developmental outcome. ~ Another disturbing issue was that the patients were examined only four times during the first year of life. Thus prolonged intervals of inadequate treatment might not have been detected for several months between examinations. Under such circumstances, it is not surprising that an athyreotic infant (deprived of any endogenous T4) would fare considerably worse than the infant with a functioning ectopic thyroid gland. A single blood specimen obtained 1 week before testing of a 7½- or 9½-year-old child is an unreliable marker for adequacy of treatment during the first year of life. We contend, on the basis of several studies, 24 that early and adequate treatment, including frequent monitoring, will ensure optimal outcome in all children with hypothyroidism, regardless of type. We quote an earlier statement: "Physicians must be dissatisfied with less than normal performances by patients whose hypothyroidism was treated early as a result of neonatal screening. ''5 To think otherwise could instill an air of futility in the management of such patients and thus result in a self-fulfilling prophecy. Marvin L. Mitchell, MD New England Regional Newborn Screening Program State Laboratory Institute Jamaica Plain, MA 02130 Robert Z. Klein, MD Department of Pediatrics Dartmouth Medical School Lebanon, N H 9/35/62073
The Journal of Pediatrics
REFERENCES
1. New England Congenital Hypothyroidism Collaborative. Effects of neonatal screening for hypothyroidism: prevention of mental retardation by treatment before clinical manifestations. Lancet 1981;2:1095-8. 2. Illicki A, Larsson A. Psychomotor development of children with congenital hypothyroidism diagnosed by neonatal screening. Acta Paediatr Scand 1988;77:142-7. 3. Heyerdahl S. Follow-up study of hypothyroidism in Norway. In: Delange F, ed. Research in congenital hypothyroidism. New York: Plenum Press, 1989;298-9. 4. Dubuis JM, Richer F, Glorieux J, et al. Should all patients with congenital hypothyroidism (CH) be treated with 10-15 ~tg/ kg/day of levothyroxine (T4)? [Abstract]. Pediatr Res 1994;572:98A. 5. New England Congenital Hypothyroidism Collaborative. Elementary school performance of children with congenital hypothyroidism. J PEDIATR 1990;116:27-32.
Reply To the Editor: Drs. Mitchell and Klein contend that early and adequate treatment will ensure optimal outcome in all children with hypothyroidism. Our observation that some patients with congenital hypothyroidism (CH) detected by neonatal screening have a less favorable cognitive and motor outcome is interpreted as disheartening news for physicians. Drs. Mitchell and Klein seem to have just one explanation: it cannot be the patient, so it must be the doctor. and they demand proof that our patients with CH were treated adequately. We consider it a blessing that in the 1970s a group of North American investigators, among them Drs. Mitchell and Klein. showed that the devastating effects of CH are preventable by introducing neonatal mass screening. In those days it was thought that fetal hypothyroidism had little or no impact on cerebral development, because early-treated patients had such favorable outcomes. Moreover, it was thought that there was no significant maternal-fetal transfer of thyroid hormone, and it was argued that a fetus could develop properly even in the absence of any thyroid hormone. Now we know that thyroxine (T4) passes the placenta. and we are aware of the devastating effects of maternal hypothyroidism on the developing central nervous system. The fetal brain needs thyroid hormone, although the questions of when and how much remain to be answered. It is hard to believe that the limited maternal supply of Ta is sufficient in all cases of severe CH: we have demonstrated that T4 levels in cord blood from infants with a complete inability to produce T4 show considerable variation.1 and that especially in severe CH, plasma T4 concentrations decrease during the first few weeks after birth In our opinion, one can hardly expect all children with CH to have completely normal motor skills and intelligence even when they are treated early and adequately.
April 1995
673
Motor and cognitive development in children with congenital hypothyroidism To the Editor: We appreciate the difficulty in conducting a long-term follow-up study of children with congenital hypothyroidism such as the one reported by Kooistra et al. (J PEDIA'rR 1994;124:903-9). The article concludes that hypothyroid children with low screening thyroxine (T4) concentrations (<50 nmol/L), despite early treatment, are likely to have borderline intelligence and motor problems. If taken at face value, this implies that families with athyreotie children should be resigned to a less-than-optimal outcome. This is also disheartening news for the physician, especially if he or she is convinced that nothing can be done to prevent the cognitive and motor problems. However, before such a pessimistic (and self-defeating) attitude is allowed to overtake us, it is crucial to ask whether the children in the study were treated adequately. A careful reading of the article shows that no data confirm the authors' statement of adequate T4 replacement therapy. With the exception of the screening mean T4 values, we can find no figures relative to T4 and thyrotropin concentrations during the first year of life, when inadequate levels of circulating T4 correlate significantly with poor developmental outcome. ~ Another disturbing issue was that the patients were examined only four times during the first year of life. Thus prolonged intervals of inadequate treatment might not have been detected for several months between examinations. Under such circumstances, it is not surprising that an athyreotic infant (deprived of any endogenous T4) would fare considerably worse than the infant with a functioning ectopic thyroid gland. A single blood specimen obtained 1 week before testing of a 7½- or 9½-year-old child is an unreliable marker for adequacy of treatment during the first year of life. We contend, on the basis of several studies, 24 that early and adequate treatment, including frequent monitoring, will ensure optimal outcome in all children with hypothyroidism, regardless of type. We quote an earlier statement: "Physicians must be dissatisfied with less than normal performances by patients whose hypothyroidism was treated early as a result of neonatal screening. ''5 To think otherwise could instill an air of futility in the management of such patients and thus result in a self-fulfilling prophecy. Marvin L. Mitchell, MD New England Regional Newborn Screening Program State Laboratory Institute Jamaica Plain, MA 02130 Robert Z. Klein, MD Department of Pediatrics Dartmouth Medical School Lebanon, N H 9/35/62073
The Journal of Pediatrics
REFERENCES
1. New England Congenital Hypothyroidism Collaborative. Effects of neonatal screening for hypothyroidism: prevention of mental retardation by treatment before clinical manifestations. Lancet 1981;2:1095-8. 2. Illicki A, Larsson A. Psychomotor development of children with congenital hypothyroidism diagnosed by neonatal screening. Acta Paediatr Scand 1988;77:142-7. 3. Heyerdahl S. Follow-up study of hypothyroidism in Norway. In: Delange F, ed. Research in congenital hypothyroidism. New York: Plenum Press, 1989;298-9. 4. Dubuis JM, Richer F, Glorieux J, et al. Should all patients with congenital hypothyroidism (CH) be treated with 10-15 ~tg/ kg/day of levothyroxine (T4)? [Abstract]. Pediatr Res 1994;572:98A. 5. New England Congenital Hypothyroidism Collaborative. Elementary school performance of children with congenital hypothyroidism. J PEDIATR 1990;116:27-32.
Reply To the Editor: Drs. Mitchell and Klein contend that early and adequate treatment will ensure optimal outcome in all children with hypothyroidism. Our observation that some patients with congenital hypothyroidism (CH) detected by neonatal screening have a less favorable cognitive and motor outcome is interpreted as disheartening news for physicians. Drs. Mitchell and Klein seem to have just one explanation: it cannot be the patient, so it must be the doctor. and they demand proof that our patients with CH were treated adequately. We consider it a blessing that in the 1970s a group of North American investigators, among them Drs. Mitchell and Klein. showed that the devastating effects of CH are preventable by introducing neonatal mass screening. In those days it was thought that fetal hypothyroidism had little or no impact on cerebral development, because early-treated patients had such favorable outcomes. Moreover, it was thought that there was no significant maternal-fetal transfer of thyroid hormone, and it was argued that a fetus could develop properly even in the absence of any thyroid hormone. Now we know that thyroxine (T4) passes the placenta. and we are aware of the devastating effects of maternal hypothyroidism on the developing central nervous system. The fetal brain needs thyroid hormone, although the questions of when and how much remain to be answered. It is hard to believe that the limited maternal supply of Ta is sufficient in all cases of severe CH: we have demonstrated that T4 levels in cord blood from infants with a complete inability to produce T4 show considerable variation.1 and that especially in severe CH, plasma T4 concentrations decrease during the first few weeks after birth In our opinion, one can hardly expect all children with CH to have completely normal motor skills and intelligence even when they are treated early and adequately.
April 1995
673