Does the dopamine transporter protein allele predict growth hormone testing results or response to growth hormone therapy?

Animal studies have shown dopamine transporter protein (DAT1) knock out mice are growth retarded and hyperactive. DAT1 has been researched in several human psychiatric studies with varying results regarding phenotype and DAT1 alleles. However, the relationship between DAT1 and short stature in humans has not been explored. Buccal swabs were collected from patients receiving growth hormone (GH) therapy and were genotyped for variable number tandem repeat (VNTR) by polymerase chain reaction. Forty subjects were included; twenty-three patients had the 10/10 DAT1 genotype and thirteen had the 9/10 genotype. Fifteen of the patients with the 10/10 genotype tested GH deficient. Seven patients with the 9/10 genotype tested GH sufficient. The linear growth rate during the first year of GH therapy was equivalent in both genotypes. In conclusion, polymorphisms in the DAT1 40 base pair (bp) VNTR genotype do not predict GH deficiency or response to GH therapy in short children.