Pituitary Dwarfism in Dogs

The effects are not only on the outside because the deficiency of the growth hormone causes underdeveloped kidneys leading to renal failure, underactive thyroid glands producing dullness and slow intelligence, and most dogs with pituitary dwarfism are sterile. Without treatment, your dog will have a shorter than normal lifespan of about four or five years. Treatment increases the lifespan and helps give your dog a better quality of life.

Pituitary dwarfism is an autosomal disorder that is inherited in some breeds such as German Shepherds, Weimaraners, Spitz, Dachshunds, Corgis, Basset Hounds, Saarloos Wolfdogs, and Czechoslovakian Wolfdogs. However, this disorder can also be caused by a tumor, infection, or cysts such as the Rathke’s pouch. The side effects are often noticed in the first few months as short legs, long body, a short jaw, bulging eyes, and skin disorders including baldness and bacterial skin infections.

If your dog has pituitary dwarfism, you will most likely notice that he is growing more slowly than he should. The symptoms depend on the breed and type of dwarfism. Some of the commonly reported signs seen in the first few months include:

• Body is longer than normal
• Legs shorter than they should be
• Bulging eyes
• Swollen abdomen
• Tongue sticks out of mouth
• High pitched puppy bark
• Short jaw and underbite (upper teeth behind the lower teeth)
• Larger than normal head
• Feet turn outward
• Swollen joints
• Bowed front legs
• Not growing at the proper rate or proportion
• Smaller than littermates
• Lack of teeth (slow to develop)
• Hair coat is not growing in like it should (not growing the long adult coat)
• May seem slower mentally than the other pups
• Panting more than usual
• Breathing difficulty
• Snoring
• Hair loss
• Darkened skin
• Small testicles

 Types

• Pituitary dwarfism (presents between 8-16 weeks) and is hereditary in many breeds such as German Shepherds, Weimaraners, Spitz, Dachshunds, Corgis, Basset Hounds, Saarloos Wolfdogs, and Czechoslovakian Wolfdogs
• Adult-onset growth hormone-responsive dermatosis

The cause of pituitary dwarfism is the lack of growth hormone produced by the pituitary gland. This may be caused by several factors, such as:

• Hereditary
• Tumors
• Infections
• Cysts
• Lack of development

Even though it may seem obvious to you by looking at your dog, the veterinarian will have to do specific tests to confirm the diagnosis of pituitary dwarfism. But first, the veterinarian has to do a complete physical assessment including auscultation and palpation, weight, height, temperature, pulse, and respiration. Endocrine tests must be done such as the plasma insulin-like growth factor-1 concentration, which will be much lower than normal. A growth hormone stimulation test is also important using a growth hormone releasing hormone (GHRH) or clonidine.

Also, measuring insulin growth factors (IGF) can determine if the levels are decreased, which they will be if your dog has pituitary dwarfism. The veterinarian will also want to check the levels of the thyroid stimulating hormones (TSH), follicle stimulating hormones (FSH), prolactin (PRL), and adrenocorticotropic hormone (ACTH). Other routine blood tests will be performed as well to rule out underlying illnesses or diseases such as cancer or infections. An MRI or CT scan can be done to check for intrapituitary cysts, which are a common cause of pituitary dwarfism.

Treating pituitary dwarfism depends on the cause of the disorder but it mostly involves replenishing the hormones that are missing. Unfortunately, there is no canine growth hormone available for treatment but there are other options available for therapeutic use. Some of those options include porcine growth hormone, progestins, or thyroid hormones.

Porcine (Pig) Growth Hormone

Porcine (pig) growth hormone can be used instead of canine growth hormones but it is very expensive. The results are variable, but they are generally not reliable.

Progestins

Progestins such as with medroxyprogesterone acetate (MPA) or proligestone are steroidal drugs that stimulate the production of growth hormones from mammary duct cells. The progestin should be given every three weeks for several months, gradually tapering off to every six weeks. This treatment can be successful although it has a few side effects such as diabetes mellitus and allergic reaction.

Thyroid Hormones

Synthetic levothyroxine has been found to have some success in treating this disorder. However, the metabolism and absorption are variable and must be monitored and adjusted carefully by the veterinarian.

Surgery

Tumors and cysts may be able to be removed surgically. This can only be done if the tumor or cyst is in an operable area and is not too close to the thyroid or other important organs. X-rays, ultrasound, MRI, and CT scans will be used to determine if the area is operable.

Without treatment, your dog will not usually live past the age of four and their quality of life will be poor. Although, with a good treatment plan, their life will be extended and the quality is much better. However, you will have to continue the treatments for the remainder of your dog’s life and it can be expensive.