There are several different types of dwarfism and I will attempt to describe some of them and if possible, provide pictures where possible.  First of all,  we must understand that all types of dwarfism are a direct result of the pituitary gland and the fact that it is not functioning properly or adequately.

Dwarfism is a condition of abnormally small stature, and is usually characterized by altered body proportions.  Dwarfism is hereditary in many breeds, most notably the German Shepherds, Weimaraners and Spitz.

Dachshunds, Basset Hounds and Welsh Corgis are an example of achondroplastic dwarfs in that they have more or less normal sized torsos and heads but with shortened legs and are typical of their breed. 

Achondroplastic dwarfism is an inherited disorder that causes short stature. It is the most common form of short-limbed dwarfism. 

Brachiocephalic dwarfism is seen in Pugs, Basset Hounds, Shih Tzu, Boston Terrier, Bulldog, Pekinese, Pomeranians.  

Miniature Poodles are subject to pseudochondroplastic dysplasia.  This is autosomal recessive.  They may appear normal at birth then decreased growth becomes apparent by 3 weeks of age; short limbs with enlarged epiphysis (the growth area near the end of a bone). 

Chondrodysplasia is a genetically-determined skeletal disorder occurring primarily in the purebred Alaskan Malamute.  This disorder involves more than simply faulty cartilage maturation. This debilitating disease is actually a birth defect causing the dog’s upper foreleg to become overly massive, short, and twisted. It is not ‘dwarfism’ nor is it ‘dysplasia’ in the true sense of the word.  It is transmitted as a simple autosomal recessive trait (meaning it is not sex-linked).  In the Alaskan Malamute,  both achondroplatic dwarfism and hemolytic anemia are inherited as pleiotropic conditions meaning a single gene will give multiple phenotype effects.  Hemolytic anemia is a disease process that destroys the red blood cells in the bloodstream.  Pleiotropic is a scientific name enabling a single gene to affect several phenotypeic traits simultaneously … a phenotypic trait is one that is visible or readily apparent upon examination whereas a genotypic trait is one on the molecular level that would require molecular analysis to define.  (an example would be :  a gene mutates and causes it’s carrier to have hair loss.  The genotype would be the genetic construction of the mutant gene and the phenotype caused would be the visible hair loss).  Typically, these dogs looks normal at birth, then short long bones, thick growth plates, may have focal squashed appearance at 7-10 days. They usually have short legs with normal body length, skull and spine.  

Pituitary dwarfism or also referred to as Hyposomatotrophism. Very simply it means that the pituitary gland does not produce or stimulate enough of the growth hormone (GH).  The pituitary gland is located at the base of the brain and this gland normally secretes hormones that are necessary for normal growth and development. Dogs with this condition may also be deficient in other hormones that the pituitary gland controls part of the process of stimulating the hormone’s production,  therefore should be checked for hypothyroidism and hypoadrenocorticism.  Pituitary dwarfism is most common in German Shepherd (an an autosomal recessive trait) but has also been reported in other breeds such as the Karelian Bear dog as well, but the mode of inheritance has not been determined for other breeds other than the GSD.  This disorder must be distinguished from other conditions that may lead to stunted growth including malnutrition, congenital hypothyroidism and other congenital conditions. 

The current belief is that the pituitary deficiencies are caused by a dysgensis of the pituitary, meaning the abnormal or defective development of an organ such as the gonads or testicles.  The gonads secrete a hormone called androgens or more commonly known as testosterone.  The testicles or gonads are controlled hormonally by the luteinizing hormone (LH) and follicle-stimulating hormone (FSH) which is secreted by the anterior pituitary gland. The anterior pituitary gland’s excretion of LH and FSH are controlled by the hypothalamus’s gonadotropin-releasing hormone.  

Breeders or owners will usually notice abnormalities by 2 or 3 months of age.  The signs caused by a deficiency of pituitary growth hormone include :  slow growth rate, retained puppy coat and eventual bilateral baldness, darkening of the skin, delayed eruption of permanent teeth, suppressed immune responses, and an altered mental state.  These pups are proportionate dwarves in that they are of small stature but with normal proportions and often have a very shrill bark. Some abnormalities in bone growth lead to a deformed appearance to the legs.  Usually other hormones produced by the pituitary gland are also decreased causing abnormalities in thyroid, adrenal and testicular function.  These dogs usually have a shortened lifespan.  

Needless to say,  parents of affected pups should NOT be bred nor should the affected pups be bred.  

Dogs with pituitary dwarfism can be treated with human growth hormone (GH) but it is very expensive and may be very difficult for a vet to get. Treated dogs should also be monitored for diabetes mellitus which is a potential side effect of (GH) therapy.  

To learn more about Pituitary Dwarfism in the German Shepherd Dog, go to http://www.dogstuff.info/dwarfism_lanting.html.