Growth Hormone-Responsive Dermatosis
Growth Hormone-Responsive Dermatosis is a poorly understood skin disease in adult dogs. Although the disease has been reported in many breeds, the Chow Chow, Pomeranian, Miniature Poodle, Toy Poodle, Keeshond and Samoyed are most often affected, suggesting a genetic basis for this disorder. Growth hormone (GH) is a pituitary hormone responsible for regulating the body's growth rate. In most affected dogs the concentration of GH in blood is low and does not increase following artificial stimulation of the pituitary gland. Male dogs seem to suffer from this disease more often than female dogs.
The clinical signs are believed to be caused by a deficiency of GH and usually develop in young animals of 2 to 5 years of age. These signs consist entirely of symmetrical hair loss on the trunk, neck, ears, tail and thighs. The skin gradually turns black in areas affected by the loss of hair. The dogs are otherwise normal.
Diagnosis & Treatment
The cause is unknown. Of the possible explanations, a lesion of the pituitary gland or disorders of hormone-stimulating organs are suspected. A diagnosis of the GH-resposive dermatosis is based on documenting GH deficiency with a GH stimulation test as well as demonstrating a beneficial response to a GH replacement therapy. Skin biopsy specimens from the affected dogs may reveal decreased-to-normal epidermal thickness and decrease in size of hair follicles (follicular atrophy) compared with normal-coated dogs.
Treatment relies on administration of synthetic human GH. Unfortunately, human GH is quite expensive and can be difficult to obtain. Regrowth of hair is used to assess response to therapy which usually occurs within 4 to 6 weeks of initiating treatment. Some dogs respond favourably to the administration of recombinant human somatotropin, while other mature dogs with or without alopecia may show no response or only a weak response of plasma GH to stimulation with GH.
- Mordecai Siegal. UC Davis Book of Dogs: The Complete Medical Reference Guide for Dogs and Puppies.
- Schmeitzel LP, Lothrop CD Jr. Hormonal abnormalities in Pomeranians with normal coat and in Pomeranians with growth hormone-responsive dermatosis.