Canine Growth Hormone Disorder (Pituitary Dwarfism) – NAVLE Study Guide

Overview and Clinical Importance

Pituitary dwarfism (also known as juvenile-onset panhypopituitarism or combined pituitary hormone deficiency [CPHD]) is a rare, inherited disorder characterized by deficiency of growth hormone (GH) and other anterior pituitary hormones. This condition results from failure of the pars distalis of the pituitary gland to develop properly during gestation, leading to proportionate dwarfism and multiple endocrine deficiencies.

This endocrinopathy is clinically significant because affected dogs present with distinctive physical features, dermatological abnormalities, and progressive organ dysfunction. Understanding the pathophysiology, diagnosis, and treatment options is essential for the NAVLE, particularly recognizing breed predispositions and the classic clinical presentation.

Etiology and Pathophysiology

Genetic Basis

Pituitary dwarfism in German Shepherd Dogs and related breeds is caused by a simple autosomal recessive mutation in the LHX3 gene located on chromosome 9. LHX3 encodes a LIM homeodomain transcription factor essential for pituitary gland development. The specific mutation involves a 7-base pair deletion in intron 5 of the LHX3 gene, which reduces the intron size to 68 base pairs. This contraction leads to deficient splicing of the LHX3 transcript, resulting in aberrant mRNA and failure of normal pituitary cell differentiation.