Pituitary Dwarfism in Dogs
Pituitary Dwarfism is an autosomal recessive inherited disorder and is encountered most often in the pastoral breeds particularly the German shepherd dog where 20% are now estimated to carry the faulty gene. The pituitary is a hormone producing endocrine gland at the base of the brain this pea-sized gland is composed of the anterior lobe and the posterior lobe. The anterior pituitary synthesizes many of the essential hormones which are then secreted for numerous body functions such as growth, reproduction, lactation and metabolism
Hormones secreted by the pituitary gland:
· Growth hormone (GH), which is essential for growth
· Thyroid Stimulating Hormone (TSH), which regulates thyroid function
· Prolactin (PRL), which is essential for lactation
· Follicle Stimulating Hormone (FSH)
· Luteinizing Hormone (LH), which is essential for ovulation in female dogs and sperm production in male dogs
· Adrenocorticotroph Hormone (ACTH), which stimulates the adrenal cortex
· Endorphins – pain receptors in the brain
· Antidiuretic Hormone ADH – kidney tubules
· Oxytocin – uterine muscles and mammary glands
Any defect in the development of the pituitary gland creates enormous problems for the dog the most obvious example of hormone deficiency is the small stature but there are also many hidden problems. Dogs that are carriers of the recessive gene do not have any visible symptoms and look exactly the same as the dogs that are not carriers and this is the problem. Pituitary dwarfism is a recessive disorder of a single gene located on chromosome 9, the birth of an affected dog means that both parents are carriers each with a single copy of the gene and of course with a recessive gene when two carriers are mated on average 50% of their progeny will be carriers and 25% of their offspring will be dwarves.
Pituitary dwarfs are in proportion but significantly smaller than their healthy littermates they do not display shortened deformed legs as is commonly assumed this is achondroplasia (a full sized dog with severely shortened legs). Another visual clinical symptom of pituitary dwarfism is that dwarves retain their puppy coat much longer than normal however in their first year the coat will be lost and the animal will become bald (alopecic) except for head and lower legs without treatment of GH.
This lack of growth and abnormal retention of the puppy coat will be mostly noticed by 2 to 3 months of age by the novice breeder/owner, an experienced breeder should be able to spot a dwarf much earlier particularly if a breeder has had prior exposure to this condition. When the dog loses its puppy coat, the skin can become squamous (scaly) and hyperpigmented that is the skin becomes much darker in colour than normal (blackened) and due to their lowered immunity, dwarfs can be prone to deep bacterial skin infections.
The clinical symptoms are not limited to the visible appearance of dwarves; they suffer from a whole range of conditions particularly from under development of the liver and kidneys causing chronic renal failure to cardiovascular problems. The deficiency of Thyroid Stimulating Hormone results in an underactive thyroid gland causing many animals to be slow and dull additionally the reduced level of gonadotrophins may result in failure of one or both testis to move or "descend" into the scrotum (cryptorchidism) in male dwarves while female dwarves do go into heat, but they do not ovulate.
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, FSH, LH and Prolactin. If canine growth hormone was available then this would be used to treat dwarves but this is not available so animals are treated with porcine GH which makes a good alternative. Without proper treatment, the long term survival rate is poor, many dwarves will not live to more than 3 to 4 years of age. However, some dogs do live longer, probably because in some cases the pituitary gland still produces a very small amount of hormones. Although treatment can improve the quality of a dog’s life significantly, sadly it cannot cure them.
Unfortunately the common misconception is that Pituitary Dwarfism is very rare but this is not the case, it affects many dogs worldwide. It would be unfeasible to test all dogs as some are more prone than others, what is not known is how many of the reported pastoral breeds such as Collies, Australian Shepherd, Samoyed and to a lesser extent outside this group Spitz, Labradors, Irish Setters and Weimaraners to name but a few actually really do have pituitary dwarfism and not some other form of dwarfism or condition, as yet PD reports are unconfirmed in other breeds. What is known is that 20% of German Shepherds and their derivatives such as the Saarloos wolfhound, the Czechoslovakian wolf dog are now carriers of PD which is much higher that might be expected for an apparently rare condition. The result is 90% of all PD affected dogs die in the womb or shortly after birth and are seen as fading puppies but of course some survive and are often sold before the condition is recognised, their life span can be severely shortened, average age 4 years, however many can live very much longer with known recorded examples up to 12 and 13 years of age.
The latest research from the University of Utrecht shows that neurological symptoms (abnormal cervical vertebrae) are likely to be present in dwarves. Neurological complaints have been found to be caused by instability in the spine at the first and second vertebrae which can result in pressure on the spinal cord producing pain, paralysis or sudden death, therefore the issues surrounding Pituitary Dwarfism must be taken very seriously when breeding. This is an incurable illness which should be prevented as a priority but in order to do so, two carriers of this recessive gene should not be bred from and because as already mentioned visually a carrier cannot be distinguished from a non carrier judgement cannot be made on appearance a genetic test is required. After 15 years of intensive research at the Department of Clinical Sciences of Companion Animals of Utrecht University, this test has been available since 2008 and is one of the few available for genetic conditions. If this DNA test would be used for all suspected breeding animals then occurrences of pituitary dwarfism would be significantly reduced.
The genetic test requires 4 ml. of blood (collected in an EDTA containing tube). The blood sample then should be sent to:
Dr. Hans S. Kooistra - Department of Clinical Sciences of Companion Animals, Faculty of Veterinary Medicine,
Utrecht University - Yalelaan 108 - 3584 CM Utrecht
[email protected]
Pituitary Dwarfism is an autosomal recessive inherited disorder and is encountered most often in the pastoral breeds particularly the German shepherd dog where 20% are now estimated to carry the faulty gene. The pituitary is a hormone producing endocrine gland at the base of the brain this pea-sized gland is composed of the anterior lobe and the posterior lobe. The anterior pituitary synthesizes many of the essential hormones which are then secreted for numerous body functions such as growth, reproduction, lactation and metabolism
Hormones secreted by the pituitary gland:
· Growth hormone (GH), which is essential for growth
· Thyroid Stimulating Hormone (TSH), which regulates thyroid function
· Prolactin (PRL), which is essential for lactation
· Follicle Stimulating Hormone (FSH)
· Luteinizing Hormone (LH), which is essential for ovulation in female dogs and sperm production in male dogs
· Adrenocorticotroph Hormone (ACTH), which stimulates the adrenal cortex
· Endorphins – pain receptors in the brain
· Antidiuretic Hormone ADH – kidney tubules
· Oxytocin – uterine muscles and mammary glands
Any defect in the development of the pituitary gland creates enormous problems for the dog the most obvious example of hormone deficiency is the small stature but there are also many hidden problems. Dogs that are carriers of the recessive gene do not have any visible symptoms and look exactly the same as the dogs that are not carriers and this is the problem. Pituitary dwarfism is a recessive disorder of a single gene located on chromosome 9, the birth of an affected dog means that both parents are carriers each with a single copy of the gene and of course with a recessive gene when two carriers are mated on average 50% of their progeny will be carriers and 25% of their offspring will be dwarves.
Pituitary dwarfs are in proportion but significantly smaller than their healthy littermates they do not display shortened deformed legs as is commonly assumed this is achondroplasia (a full sized dog with severely shortened legs). Another visual clinical symptom of pituitary dwarfism is that dwarves retain their puppy coat much longer than normal however in their first year the coat will be lost and the animal will become bald (alopecic) except for head and lower legs without treatment of GH.
This lack of growth and abnormal retention of the puppy coat will be mostly noticed by 2 to 3 months of age by the novice breeder/owner, an experienced breeder should be able to spot a dwarf much earlier particularly if a breeder has had prior exposure to this condition. When the dog loses its puppy coat, the skin can become squamous (scaly) and hyperpigmented that is the skin becomes much darker in colour than normal (blackened) and due to their lowered immunity, dwarfs can be prone to deep bacterial skin infections.
The clinical symptoms are not limited to the visible appearance of dwarves; they suffer from a whole range of conditions particularly from under development of the liver and kidneys causing chronic renal failure to cardiovascular problems. The deficiency of Thyroid Stimulating Hormone results in an underactive thyroid gland causing many animals to be slow and dull additionally the reduced level of gonadotrophins may result in failure of one or both testis to move or "descend" into the scrotum (cryptorchidism) in male dwarves while female dwarves do go into heat, but they do not ovulate.
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, FSH, LH and Prolactin. If canine growth hormone was available then this would be used to treat dwarves but this is not available so animals are treated with porcine GH which makes a good alternative. Without proper treatment, the long term survival rate is poor, many dwarves will not live to more than 3 to 4 years of age. However, some dogs do live longer, probably because in some cases the pituitary gland still produces a very small amount of hormones. Although treatment can improve the quality of a dog’s life significantly, sadly it cannot cure them.
Unfortunately the common misconception is that Pituitary Dwarfism is very rare but this is not the case, it affects many dogs worldwide. It would be unfeasible to test all dogs as some are more prone than others, what is not known is how many of the reported pastoral breeds such as Collies, Australian Shepherd, Samoyed and to a lesser extent outside this group Spitz, Labradors, Irish Setters and Weimaraners to name but a few actually really do have pituitary dwarfism and not some other form of dwarfism or condition, as yet PD reports are unconfirmed in other breeds. What is known is that 20% of German Shepherds and their derivatives such as the Saarloos wolfhound, the Czechoslovakian wolf dog are now carriers of PD which is much higher that might be expected for an apparently rare condition. The result is 90% of all PD affected dogs die in the womb or shortly after birth and are seen as fading puppies but of course some survive and are often sold before the condition is recognised, their life span can be severely shortened, average age 4 years, however many can live very much longer with known recorded examples up to 12 and 13 years of age.
The latest research from the University of Utrecht shows that neurological symptoms (abnormal cervical vertebrae) are likely to be present in dwarves. Neurological complaints have been found to be caused by instability in the spine at the first and second vertebrae which can result in pressure on the spinal cord producing pain, paralysis or sudden death, therefore the issues surrounding Pituitary Dwarfism must be taken very seriously when breeding. This is an incurable illness which should be prevented as a priority but in order to do so, two carriers of this recessive gene should not be bred from and because as already mentioned visually a carrier cannot be distinguished from a non carrier judgement cannot be made on appearance a genetic test is required. After 15 years of intensive research at the Department of Clinical Sciences of Companion Animals of Utrecht University, this test has been available since 2008 and is one of the few available for genetic conditions. If this DNA test would be used for all suspected breeding animals then occurrences of pituitary dwarfism would be significantly reduced.
The genetic test requires 4 ml. of blood (collected in an EDTA containing tube). The blood sample then should be sent to:
Dr. Hans S. Kooistra - Department of Clinical Sciences of Companion Animals, Faculty of Veterinary Medicine,
Utrecht University - Yalelaan 108 - 3584 CM Utrecht
[email protected]
| dna-dwarfism-uk.pdf |
The following pages have been divided into sections, each dwarf will have all of these symptoms to varying degrees depending on the hormone levels each produces as an individual.
Pituitary Function
Secondary hypothyroidism
Growth Hormones and Treatment
Skin and Hair problems
Spinal Problems
PDA
Pituitary Function
Secondary hypothyroidism
Growth Hormones and Treatment
Skin and Hair problems
Spinal Problems
PDA
