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 wolfhounds.
German shepherd dwarfs have a combined deficiency
of GH, TSH, PRL, and the gonadotropins. In contrast, ACTH secretion
is preserved in these animals.
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 skin infections.
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 disorder.
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:
Dr. H.S.
Kooistra (H.S.Kooistra@uu.nl)
Department
of Clinical Sciences of Companion Animals
Faculty of
Veterinary Medicine, Utrecht University
Yalelaan 108
3584 CM Utrecht
The Netherlands
(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 address.
The Vet also checks the dogs microchip number
to ensure the dogs correct identity. We are not a commercial
laboratory and will not sell the test online.)
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.
Figure 1.
A 10-month-old German shepherd dwarf with lack of guard hairs
and retention of puppy hairs.
IMPORTANT INFORMATION
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
:
+44 (0)1905 830900 -
email: