Endocrine Alopecia in Cats - Page 3

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Endocrine Alopecia in Cats

By: Dr. Rosanna Marsalla

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Diagnosis In-depth

It is important to determine whether the alopecia is self-inflicted or spontaneous. Cats may spend considerable time grooming themselves while unobserved by their owners, and frequently it is not obvious whether the hair loss has been self-inflicted or spontaneous.

  • Self-inflicted hair loss is more common than feline endocrine alopecia and should be considered first.

  • Examination of the tip of the hair under the microscope helps differentiate spontaneous hair loss from a self-inflicted hair loss. In many cats with symmetric alopecia, the hair tips are broken suggesting excessive self-grooming and an underlying pruritic or itchy disease.

  • Alternatively, a plastic cone (Elizabethan collar) may be used for a few weeks to monitor hair growth. If hair regrowth occurs, self-inflicted hair loss due to an underlying pruritic skin disease should be considered.

  • Pruritic skin diseases in cats include flea allergy, atopy, food allergy, dermatophytosis (ringworm) and mange mite infestation.

  • Medical history including age of onset, seasonality, response to treatment with cortisone-like drugs such as glucocorticoids and clinical signs will help your veterinarian rank these different possible diseases.

  • All cats with symmetric alopecia should have several skin scrapings performed and hairs from affected skin should be submitted for fungal culture to identify dermatophytosis (ringworm).

  • An aggressive flea control program should be instituted. A dietary change may be appropriate in cats that do not have seasonal disease.

  • Non-pruritic skin diseases in cats include dermatophytosis (ringworm), demodectic mange, telogen effluvium (loss of hairs in resting phase from their follicles), overactivity of the adrenal glands (hyperadrenocorticism) and hypothyroidism (which is extremely rare in cats).

  • A diagnosis of feline symmetric alopecia is made by exclusion of other diseases.

  • A complete blood count and serum chemistry tests are normal in cats with symmetric alopecia.

  • Skin biopsies from affected cats show telogen hairs (hairs that are in a resting phase rather than in a growing phase).

  • These findings, however, are not specific for this condition, and most of the hairs in normal cats may be in the resting (i.e. telogen) phase.

    Treatment In-depth

  • Feline symmetric alopecia primarily is a cosmetic condition, and not treating it does not harm the general health of the cat.

  • Treatments that have been attempted in cats with symmetric alopecia have the potential to cause adverse effects. You should ask your veterinarian about the potential risks of possible medical treatments.

  • Liothyronine (a thyroid hormone also called T3) can be administered at an initial dosage of 20 micrograms per cat twice per day. The dosage is gradually increased to 50 micrograms twice per day.

  • The gradual increase in dosage is recommended to minimize possible adverse effects that may arise from an increase in cellular metabolism caused by liothyronine (T3) administration.

  • The main adverse effect of excessive liothyronine (T3) is cardiac arrhythmias, which resolve with discontinuation of the drug.

  • Hair regrowth may occur in 4 to 10 weeks.

  • A positive response to liothyronine (T3) therapy does not necessarily imply the presence of thyroid gland disease, because thyroid hormones have the ability to stimulate hair growth in normal individuals.

  • Alternatively, a combination of androgens and estrogens may be tried. Testosterone may be used at 12.5 milligrams and diethylstilbesterol at 0.625 milligrams administered intramuscularly.

  • Adverse effects that may be seen with androgen and estrogen therapy include liver toxicity, personality change, bone marrow suppression, and aggression.

  • Injections may be repeated in 6 weeks if no response is seen after the first injection.

  • Hair regrowth should begin within 2 to 4 weeks and a complete response should be observed within 2 to 3 months.

  • Relapses are not uncommon and may occur within 6 months or up to 2 years after discontinuation of therapy.

  • Additional therapy usually is successful.

  • Progesterone-like drugs (e.g. megestrol acetate, medroxyprogesterone acetate) are not licensed for this use in the United States and are not recommended due to the possibility of severe adverse effects.

  • These adverse effects include diabetes mellitus, adrenal gland suppression, and mammary gland hyperplasia or neoplasia (i.e. cancer).


    Some cases of feline symmetric alopecia are idiopathic (of unknown cause) whereas others are allergy-related. The only known underlying disease that can be prevented is flea allergy. Thus, aggressive flea control measures are strongly recommended.

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