Hyperandrogenism in Dogs
Hyperandrogenism in canines is a rare syndrome characterized by heightened levels of masculinizing sex hormones such as testosterone and its derivatives in the bloodstream. It predominantly affects intact male dogs.
In male dogs, androgens are primarily produced by the interstitial cells located in the testes. They play a pivotal role in normal male sexual development, promoting masculine behaviors and physical attributes like spermatogenesis—the production of sperm. Androgens comprise steroid hormones like testosterone, androsterone, and dihydrotestosterone, a biologically active metabolite derived from testosterone.
Dihydrotestosterone is chiefly formed in the prostate gland, testes, hair follicles, and adrenal glands. Androgens are also synthesized by the adrenal cortex, situated along the periphery of the adrenal gland near the kidneys, and by the ovaries in female dogs.
Hyperandrogenism can arise due to excessive hormone production by the testes, ovaries, or adrenal cortex. Dysfunction in enzyme activity may lead to hyperandrogenism, particularly in the adrenal cortex. Additionally, administration of synthetic androgens can induce hyperandrogenism.
Symptoms of hyperandrogenism may include behavioral alterations, reproductive tract abnormalities, and skin issues. This condition is more commonly observed in breeds such as Pomeranians, Chow Chows, Poodles, Keeshonds, and Samoyeds.
Symptoms and Types
- Aggression
- Impaired growth
- Bilaterally symmetrical hair loss affecting the neck, trunk, rear thighs, outer ear, and tail
- Dry, brittle coat
- Skin hyperpigmentation
- Dandruff
Female:
- Vaginitis
- Irregular estrous cycles
- Extended anestrus periods
- Virilization, marked by the development of male traits
- Clitoral hypertrophy
- Abnormal sexual differentiation due to in utero androgen exposure
Male:
- Enlarged prostate (prostatomegaly)
- Abnormal sperm morphology
- Hyperplasia of circumanal glands
- Prepubertal
- Premature closure of growth plates
Causes
- External administration of androgens
- Increased internal androgen production
- In utero exposure to androgens in females
- Testicular tumor, typically secondary to testicular malignancy.
Diagnosis
Your veterinarian will conduct a thorough physical examination of your dog, including blood tests such as a chemical profile, complete blood count, electrolyte panel, and urinalysis. These tests help rule out underlying metabolic conditions like hypothyroidism, hyperadrenocorticism, or hyperestrogenism. If your dog is displaying abnormal behavior, a comprehensive neurological examination will also be conducted.
Providing your veterinarian with a detailed history of your dog’s health, symptoms onset, and any relevant genetic background is crucial for diagnosis. Information about the health status of your dog’s maternal parent before and after pregnancy is particularly helpful, especially if there’s a suspected genetic link or if the disorder may have been acquired prenatally.
Abdominal radiography or ultrasound imaging may be performed to visualize the abdomen for masses or gonadal tissue, potential contributors to hyperandrogenism.
Several tests may be utilized to confirm a diagnosis:
- A karyotype, or chromosome analysis, can detect intersex/gonadal sex abnormalities.
- Serum samples will be evaluated for sex hormone levels.
- Growth hormone stimulation test.
- Serum testosterone concentration test.
- Adrenocorticotropic hormone (ACTH) stimulation test assesses adrenal response to ACTH, a hormone produced in the pituitary gland.
- Urine cortisol-creatinine ratio test helps rule out hyperadrenocorticism. Results may vary.
Treatment
It is advisable to surgically neuter intact animals, and surgical removal of any testosterone-secreting masses or abnormal tissue should be considered. Controlled destruction of the adrenal gland is another option. Administration of growth hormones may be necessary, but the specific treatment approach will depend on the underlying cause of your dog’s hyperandrogenism.
Living and Management
Following the initial treatment, your veterinarian will schedule regular follow-up appointments to monitor your dog’s progress and address any potential complications or underlying conditions. Additional ACTH stimulation tests and blood tests may be conducted to assess serum testosterone levels if they were initially elevated. Standard physical examinations will also be performed to ensure that your dog is recovering effectively from the effects of hyperandrogenism.
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