Any defect in the development of the pituitary gland may result in a
form of isolated or combined pituitary hormone deficiency. In dogs,
congenital GH deficiency or pituitary dwarfism is the most striking
example of pituitary hormone deficiency. This recessive inherited
disorder is encountered most often in German shepherd dogs, but it
has, for example, also been reported in Saarloos wolfhounds. The
genetic defect causing congenital GH deficiency in German shepherd
dogs is also the cause of pituitary dwarfism in Saarloos wolfhounds,
because the disorder in the latter breeds was first recognized after
German shepherd dogs had been used in the breeding of Saarloos
German shepherd dwarfs have a combined deficiency of GH, TSH, PRL,
and the gonadotropins. In contrast, ACTH secretion is preserved in
Dogs that are carriers of the mutated gene that causes pituitary
dwarfism do not have any symptoms and look exactly the same as their
fellow German shepherd dogs that aren’t carriers. Since pituitary
dwarfism is a recessive disorder of a single gene,
the birth of a dwarf indicates
that both parents are carriers of the mutation.
Pituitary dwarfs are significantly smaller than their healthy
littermate, but the dwarfs are in proportion. Another clinical
manifestation of pituitary dwarfism is that the dwarfs have retained
their puppy hair coat. In time, the hair coat will be largely lost
and the animal will become alopecic (bald) (Figure 1).
The growth retardation and the abnormal hair coat are mostly noticed
by 2 to 3 months of age. The hairs are easily epilated, and when the
animal loses its hair coat, the skin can become squameous and
hyperpigmented, making the skin darker in color. Furthermore, due to
a lowered local immunity of the skin, dwarfs are prone to bacterial
However, the clinical signs are not limited to exterior appearances.
The dwarfs suffer from a whole range of clinical manifestations far
worse than skin and hair coat problems. For instance, GH deficiency
also leads to underdevelopment of the kidneys, causing chronic renal
failure. The deficiency of TSH will result in an underactive thyroid
gland, causing the animals to be slow and dull. Furthermore, the
insufficiency of the gonadotropins will result in failure of one or
both testis to move, or "descend" into the scrotum (cryptorchidism)
in male dwarfs. Female dwarfs do go into heat, but they do not
ovulate. It can be concluded that pituitary dwarfism is a serious
Although the physical features of pituitary dwarfism may seem
obvious, the final diagnosis should be based on 'pituitary
stimulation tests'. These tests can detect a deficiency of GH, TSH,
prolactin, LH and FSH.
The most logical therapeutic option would be to treat the dwarfs
with canine GH and thyroid hormone. Treating the animal with thyroid
hormone is simple, but it is not possible to treat the dwarfs with
canine GH, since it is not available for therapeutic use. However,
research has demonstrated that porcine GH is identical to canine GH,
making it a good alternative for treatment.
Without proper treatment, the long term prognosis is poor. Many
dwarfs will not live more than 4 to 5 years. However, some dogs do
live longer, probably because in some cases the pituitary still
produces a small amount of hormones. Although the prognosis improves
significantly when dwarfs are properly treated, their prognosis
still remains guarded.
It should be clear that the birth of dogs with this serious illness
should be prevented. In order to do so, two carriers of this
mutation should not be bred. The problem is that, as mentioned
earlier, one cannot distinguish a carrier from a non carrier judged
on its appearance. This would require a genetic test. After 15 years
of intensive research at the Department of Clinical Sciences of
Companion Animals of Utrecht University, this test is now available!
If this test would be used for all breeding animals, pituitary
dwarfism could be completely eradicated in German shepherd dogs.
A genetic test may not seem to be of big importance to German
shepherd dogs, since the disorder seems to occur only occasionally.
However, one should keep in mind that many dwarfs die in the uterus
or shortly after birth. One should also be aware of the fact that if
just 1 percent of the German shepherd dog populations are dwarfs,
then 18 percent of the population will be carriers of the mutation.
This means that the number of carriers will be much higher than
might be expected. When 2 of these carriers are mated, on average 25
percent of their offspring will be dwarfs and half of the siblings
will be carriers of the mutation.
For the genetic test, 4 ml. of blood (collected in an EDTA
containing tube) is needed. The blood sample has to be shipped to:
Department of Clinical Sciences of Companion Animals
Faculty of Veterinary Medicine, Utrecht University
3584 CM Utrecht
(The only way the genetic test can be performed is that a blood
sample is collected by a Veterinarian, who also checks and provides
the data of the dog and the owner, including the owners full
Vet also checks the dogs microchip number to ensure the dogs correct
identity. We are not a commercial laboratory and will not sell the
costs of the genetic screening for the mutation that causes
pituitary dwarfism in German shepherd dogs are Euro 100 (excl. VAT).
In short, pituitary dwarfism is a serious, incurable illness of
which the occurrence is highly underestimated! The good news is that
there is now a genetic test with which carriers of the mutation can
be identified. If all breeding animals were tested (only once), and
a correct breeding policy would be implemented, this severe illness
could be completely eradicated.
This genetic test is only available at the laboratory of the Faculty
of Veterinary Medicine, Utrecht University, The Netherlands. The
mutation causing pituitary dwarfism first has to be published in a
scientific journal before other laboratories may start to use this
test. The publication may, however, take a year or more. In the
meantime, we do not want to keep this test away from breeders who
want to prevent dwarfs from being born. Therefore, blood samples can
now be sent to our lab for analysis.
Anyone wishing to DNA test their dog for Pituitary DWARFISM
PLEASE USE THIS FORM
Email - question
Dear Hans Kooistra,
I understood that you along with a colleague discovered the DNA test
for Pituitary Dwarfism. Could you please advise me regarding the
authenticity of this DNA TEST?
Email – reply
The only place in the world where this DNA test is performed is
Utrecht, because we are the only ones knowing the exact mutation
causing pituitary dwarfism in the GSD. Laboklin ships the samples
they get to our lab. This also explains the difference in price. If
the samples are send to our lab directly we charge Euro 100
(excluding V.A.T.), which is lower than the price mentioned in the