In the last years an increasing number of associations between single nucleotide polymorphisms (SNPs) in candidate genes and production traits have been reported in beef cattle, but very often the results were not validated and few studies considered breeds homozygous for the allele responsible for the muscular hypertrophy. Therefore, we analysed the variability of 19 previously reported SNPs in 12 genes (GH, GHR, GDF8, GHRL, IGF2, LEP, LEPR, MYF5, NPY, POMC, UCP2, UCP3) in the hypertrophic Piemontese breed and investigated the effects of the observed polymorphisms on growth and conformation. Fourteen SNPs were polymorphic and a significant linkage disequilibrium was observed between SNPs in GHR, LEP and NPY genes, for which both single-SNP and haplotype effects were estimated. Negligible effects on the investigated traits were observed for GHRL, MYF5, NPY, POMC, UCP2 and UCP3 genes. The GHR gene significantly affected daily gain and its effect was further increased when haplotypes were considered. The C allele at LEP-1 and LEP-2 had moderate negative effects on the considered traits, whereas the C allele at LEP-3 mostly had positive effects; haplotypes in the LEP gene showed weaker but favourable associations with all the traits. The C allele at IGF2 and LEPR had favourable effects on daily gain and negative effects on meat conformation traits. The associations observed for GHR and LEP were consistent with those of previous studies, providing additional evidence of their usefulness as markers. Practical aspects of the applications to the breeding programme of the Piemontese breed need to be examined.