Down syndrome : Growth and endocrine impact

Abstract: Down syndrome (DS) is associated with psychomotor retardation, short stature and endocrine dysfunction. Statural growth is a well-known indicator of health. The growth in DS differs markedly from that of other children and there is a 20 cm reduction of final height as compared to target height. We developed growth charts specific for Swedish children with DS, in order to facilitate early diagnosis of concomitant diseases that influence growth. The growth charts are available for paediatricians and child health care professionals in Sweden. The mechanism underlying the impaired growth in DS is unknown. Height is influenced by parental factors, energy intake, hormone balance and general health. In DS, genetic factors deriving from the extra chromosome 21 further affect growth. Children with DS seem to have reasonable levels of growth hormone (GH), even though GH treatment for limited periods of time improves growth velocity. Within the present project, the subjects of a previous study on early GH therapy in DS were followed up regarding late effects. We found a larger adult head circumference and better psychomotor abilities in the previously treated subjects despite a lack of effect on final height. In adult life, GH has effects on psychological well-being and metabolism. The clinical features in adults with DS might indicate impaired GH secretion. Ten young adults with DS were studied and compared with ten healthy controls. The GH secretion in the DS subjects did not differ from that in the controls. The fat body mass percentage was increased in DS, in line with the high prevalence of overweight/obesity. The finding of an increased HOMA index as well as a high relative rate of hepatic glucose production in DS indicates reduced insulin sensitivity both peripherally and in the liver. Thyroid dysfunction is common in DS. There is a 30-fold increase in congenital hypothyroidism, and acquired hypothyroidism has been reported to be present in up to 50% of adults with DS. We collected neonatal screening results and hospital records for the first ten years of life of 68 children with DS. The mean TSH concentration was increased neonatally, indicating marginal hypothyroidism early in life in DS. However, the neonatal TSH level did not predict development of manifest hypothyroidism later in life.