PITUITARY DWARFISM

What is it?

All materials on this website are under copyright 1999 DJ Hensch

Pituitary Dwarfism in the German Shepherd Dog is a rare congenital birth defect that can affect one or more pups in a litter. Pituitary dwarfism is a simple autosomal recessive gene so both parent dogs must carry the dwarf gene for dwarf pups to be produced. According to Malcolm B. Willis, Ph.D., dwarfism is a simple trait caused by a major gene and thus quite independent of normal growth genes. It is interesting to note here that in my research, after consulting several veterinarians, I was told that the odds of producing a dwarf pup again, even doing repeat breedings using the same parent dogs, will be 1 in a billion. So if I wanted to get another dwarf pup I couldn't. Now having spoken to geneticists I am told the "1 in a billion" idea is untruthful since we have only bred around 12 million GSD's since 1900 and it was 1 in a billion then so far we would have either zero or one dwarf on the planet . (Now that makes sense!!) The more accurate ratio seems to be about 1 per 100 litters based on one country's data with more reserach still being conducted. If it really is a simple recessive then you get a 1:4 or 25% chance of producing a dwarf in a repeat mating according to one geneticist. This certainly makes more sense to me. To prove this there is record of one bitch who had (at least) three litters in a row with dwarfs all to different sires. That also tends to confirm that only one parent NEEDS to be affected BUT it is probably an additive trait which can take some elements from either or both parents. This also helps to explain the wide range within the condition. Holland is currently doing research trying to determine why some litters contain more than one dwarf. Interesting also is that the information available to me from Vet books indicates that dwarfs are sterile, thus unable to reproduce. My own female dwarf GSD, Trisha, went through 2 heat cycles, the last one being confirmed when she was spayed and was found to have fully developed follicles in both ovaries. In her case she had ovaries and fallopian tubes the size one would find in a toy breed dog and her uterus was the size of a 70 pound female GSD. Had she ever been bred the pregnancy would have killed her.

Having one or more dwarfs in one's litter is a shocking discovery. Dwarf pups are usually of normal birth weight in comparison to the littermates. Many people will cull possible dwarf pups. This may be done prematurely as there is a condition prone to the German Shepherd Dog known as DD pups which is simply "delayed development" (also known as Delayed Growth Syndrome) in which the pup may appear to be a dwarf and in reality is not. A DD pup will be much smaller than its littermates until it reaches 5 months of age when the pup will suddenly (reasons unknown) begin to grow again and over the next 2 years reach normal size in comparison to its littermates. The only way known to determine a dwarf pup from a DD pup is by dentition. A dwarf pup will not have full or normal dentition whereas a DD pup will.

Neither condition is to be confused with malnutrition pups whose growth is retarded by circumstances of neglect / abuse in feeding habits or hypothyroid pups whose growth is stunted as a result of thyroid hormone deficiencies.

The cause of pituitary dwarfism is a cyst on the pituitary gland that leads to partial or total pituitary insufficiency. In some cases a dwarf can be given growth hormones that will result in some amount of growth but the dwarf will never reach normal GSD size. In the cases I am familiar with where growth hormone treatments were given the dwarf GSDs reached the size of a Shetland Sheepdog. The dwarf's haircoat, which can be long to begin with, may grow out in length through growth hormone treatments. The dwarf also developed diabetes melitis and had seizures. The problem here is growth hormone alone is unlikely to do much good - could even make things WORSE because there is no growth hormone for canines. The dwarf mentioned above was given human growth hormone treatments. So there are no real answers in this direction as of yet.

The life expectancy of a dwarf is said to be 2 years at best according to Vet books. I know of one dwarf GSD who lived to be 13 years old outliving all her littermates. So obviously there is some controversy over the age limit. I have many recorded cases of dwarf GSDs living beyond the 2-year age (and without the benefit of growth hormone treatments). My dwarf GSD, Trisha, (whelped 4/94) is currently 4 years and 9 months old as of this writing.

This page last updated on May 13, 1999