Vets, Hormones, and Hair Loss

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VISITING VET

The hair of the dog

March 5, 2005

By Gerhard Jasny, VMD

Tank is a little Boston Terrier who first came to my office at eight months

old. He had been licking his groin and developed a condition, not serious

but uncomfortable, called scrotal pyoderma. Topical medication cleared the

infection right up, but three months later he was back with an itchy rash on

his neck. This time the infection was deeper and we opted for oral

antibiotics, fatty acid supplements, and a teensy bit of cortisone to calm

down the inflammation and pruritus (the technical term for itchiness). Three

weeks later, Tank was back. What now? The rash on his neck had cleared but

he was losing hair on his belly and the inside of his hind legs. He was

almost completely bald on his underside and the coat on his neck was also

getting thin. Unlike the other episodes, there was no evidence of infection.

Tank wasn't pruritic. In fact, his skin didn't look irritated at all. No

bumps, no redness, no dandruff. Just no hair.

Clients often complain that their animals are shedding excessively. Usually

their concern is unwarranted. As long as the skin looks healthy and there

are no bald spots, it's probably normal physiologic shedding. You need a

vacuum, not a vet. Alopecia is defined as the loss or lack of hair, ranging

from small, localized areas to complete baldness. If there are patches where

the hair is thin and a rough stubble when you rub your hand over it, this is

“self-induced alopecia,” caused by the animal chewing out its own fur in

response to itching from allergies, parasites, or bacterial or fungal

infections. Tank's bald spots had no stubble. They were clearly not

self-induced and the hair loss was way beyond normal shedding. Bilaterally

symmetrical hair loss is often a symptom of endocrine abnormalities, such as

an underactive thyroid, adrenal gland disease, or sex hormone imbalance. But

Tank was very young to be experiencing any of these conditions, and he was

showing no other signs except hair loss. His healthy skin, the symmetrical

distribution of the hair loss, his young age, and his purebred status sent

up a little red flag. I went to my on-line veterinary data base and punched

in “Boston Terrier Alopecia.” I browsed the results.

Causes of hair loss

Canine recurrent flank alopecia: a repeated seasonal hair loss on the sides

of the body, common in English Bulldogs, Airedales, and boxers but occurring

in many breeds. It may happen every year, every few years, or only once. In

our part of the world, most cases lose their fur in the fall and re-grow in

spring or summer, but some do just the reverse. The bald areas will often

have excessive pigmentation. No one knows the cause, but it is suspected

that there is some abnormal response of the hair follicles on the flank to

changing day length. Interesting, but not Tank. Color Dilution Alopecia

(CDA) and Black Hair Follicular Dysplasia (BHFD) are two uncommon, inherited

abnormalities that are specifically associated with certain coat colors. In

CDA, most prevalent in blue or fawn Dobermans but reported in at least 11

different breeds, hair loss is confined to area of blue or fawn colored coat

It occurs between three months and three years of age. BHFD can begin as

young as one month of age, manifested by hair loss in the black portions of

two- tone or three-tone coated dogs. It has been reported in seven different

breeds. Dogs with these syndromes are prone to secondary bacterial

infections and seborrhea. Other breeds, including Irish Water spaniels,

Bouviers, Staffordshire terriers, miniature schnauzers, English springers,

Chesapeake Bay retrievers, Labrador retrievers, rottweilers, and French

bulldogs, can be affected by a variety of hair follicle abnormalities

unrelated to coat color. Siberian husky and Alaskan malamute pups may lose

the long “guard hairs” on their trunks, but not their heads or legs, leaving

them with a funny ruffed appearance. The texture of the fur may be abnormal,

with a reddish discoloration. Northern breed dogs are also prone to a

condition veterinarians hate, post-clipping alopecia. If we shave an area on

a samoyed, chow, malamute, or husky, the fur may take a very long time to

re-grow, as long as two years in some cases. This is because these

heavy-coated Northern dogs normally have a very long hair cycle. Rather than

shedding and re-growing a full coat every year like dogs from more temperate

climates, they shed their coats less frequently, and their follicles remain

in a quiescent state for prolonged periods of time. Portuguese water dogs

and curly-coated retrievers have a syndrome, occurring between the ages of

two and four years in which they lose hair on their trunks. When, and if, it

re-grows, it often has an abnormal texture. All of these syndromes result

from abnormalities of the hair follicles and may be diagnosed by a

combination of clinical signs, breed, history, and skin biopsy (which should

be evaluated by a pathologist who is specially trained in dermatological

disorders).

Time for Rogaine?

Now I came to the section on Pattern Baldness. The hair follicles of dogs

with pattern baldness may be histalogically normal. They just don't grow

hair in specific regions. For example, pinnal alopecia of dachshunds. I've

seen that. They lose the hair on the ears, starting at about a year of age.

By the time they are middle-aged their ears are bald and hyper-pigmented.

Next. Ventral pattern alopecia. Typical age of onset: six months. Tank was

11 months. Close enough. Usually affecting the areas behind the ears, the

entire belly from neck to tail and the insides and backs of the thighs. Yup.

Breeds most commonly affected: dachshunds, chihuahuas. whippets, greyhounds,

Italian greyhounds, miniature pinschers, Manchester terriers and…drum roll…

Boston terriers. Bingo! I did a little dance and went back to the exam room.

“Looks like Tank has ventral pattern alopecia!” I informed her,

enthusiastically.

“What's that?” she asked. “Well, it's this thing Boston terriers can get,” I

began. “…um…this condition, you know, where they get bald…ventrally…that

means underneath.”

I paused. She looked at me expectantly. She didn't exactly say “Duh,” but I

suspect she was thinking it. “What causes it?” she asked. Another pause.

“It just happens,” I replied, lamely. “Ah,” I rallied, “but I do know how to

treat it!”

Many of these syndromes are primarily cosmetic. They bother the person looking

at the dog more than they bother the dog, and sometimes simply waiting is the

answer, as with post-clipping alopecia and canine recurrent flank alopecia. But

we always want to try to improve the coat if possible. Melatonin, a hormone

produced by the pineal gland in the brain, is naturally involved in the hair

growth cycle, signaling the body to respond to decreasing day length by growing

a winter coat. You can buy melatonin over the counter at any health food store

and many dogs with these conditions will respond to it well. The dose varies

with the size of the dog. Once hair has re-grown, you can attempt to wean the

dose down, but most dogs will lose hair again if you discontinue it entirely.

CDA and BHFD are the more difficult to treat, needing antibiotics and medicated

shampoos to treat the infections and seborrhea that often develop. Sometimes a

change in food can help, especially eliminating soy. Sometimes using synthetic

retinoids can promote hair growth, but melatonin is the cornerstone of therapy

for most of these conditions. Now if your middle-aged mutt is covered with big

itchy hairless patches, please don't just go buy melatonin. Go to your

veterinarian for a diagnosis. The syndromes described above are not that common

and occur almost exclusively in young, purebred dogs. Your pruritic mixed breed

dog probably has fleas, mange, allergies, an underactive thyroid, Cushing

disease, Sertoli cell tumor, or something else, and no amount of melatonin is

going to help. Tank, however, was a classic case of ventral pattern alopecia.

Within three months of starting his melatonin, he had a beautiful full coat. Ah,

success.