On Sniff, IGF1 is treated as the canonical dog body-size locus (Sutter 2007): a representative SNP in the IGF1 gene body on chromosome 15 tags a haplotype enriched in small breeds versus giant breeds.
Atlas-wide allele frequency is about 55 percent across 13,409 dogs with data in 197 breeds. High frequency at this tag means the allele is common in the small body-size pool; low frequency means it is common in the giant pool. Intermediate breed frequencies sit in between.
This is a morphology allele-frequency page, not a Mendelian disease call. A trait SNP is a tag, not a clinical verdict for an individual dog.
Honest abstention: production Ask, when routed only through the OMIA documented-disease atom layer, did not detail IGF1 molecular function from those atoms. The grounded home for this question is the IGF1 gene page (and the human ortholog pointer OMIM 147440 where comparative context helps).