Dear Dr. Fox:

My German shepherd mix is about 3.

Until recently, she was friendly, outgoing and trustworthy. But now it’s like a shadow comes over her, and she gets spooky and snappy. She pants a lot, gets sweaty and seems possessed. She also scratches more than she used to.

I thought of obedience school after the vet couldn’t find anything wrong with her. He suggested trying Prozac if she does not improve.

M.W., Houston

DF: Ruling out some backyard trauma while she was out and you were not present or a change in the home social environment, I would ask your veterinarian to run a full thyroid profile.

Thyroid dysfunction causing aberrant behavior and seizures is reaching near epidemic proportions in dogs, according to my friend W. Jean Dodds. The disease afflicts young dogs such as yours that show behavioral changes, including seemingly schizophrenic behavior.

Some breeds are especially prone, notably the German shepherd, Doberman pinscher, English springer spaniel, Akita, golden retriever, Rottweiler and Shetland sheepdog. Hereditary autoimmune destruction of the thyroid gland accounts for 90 percent of cases of hypothyroidism in purebred and hybrid dog breeds, Dodds says.

After blood tests to confirm the diagnosis, Dodds recommends treatment twice daily with thyroxine at a dose level according to your dog’s weight. Relief should be evident in a few days.

There are many chemical contaminants in our environment, food and water that are identified as endocrine disrupters, which I believe could play a significant role in this near epidemic.

Dear Dr. Fox:

My indoor/outdoor house cat, Lil Bit, is 8 or 9. She has always had vomiting issues.

In the past, it was once every three to four days and usually first thing in the morning. I blamed it on her eating too fast.

Within the past couple of months, it has gotten worse. Now she vomits just about every time she eats. She has lost quite a bit of weight, and her fur is no longer sleek and shiny.

I have tried different cat foods. Nothing seems to help.

I thought maybe it was an issue with fleas. She now wears a flea collar all the time, but she is still having vomiting issues.

M.C., Bridgeport, Conn.

DF: First, take off the flea collar. Fleas don’t make cats vomit.

This “morning sickness” could indicate a serious health issue, such as feline viral lymphoma. But it is most likely because Lil Bit is eating too much too fast during her first meal of the day. So give her a teaspoon of food when you get up and a tablespoon when you leave for work.

Be sure there is no corn in her diet. Many cats are allergic to corn, which has no place in any pet food.

She might be allergic to, or intolerant of, other ingredients. Give her Gerber’s baby food — beef, turkey or chicken — and then better foods, such as Organix or Wellness.

Try home-prepared cat food. Preparing your own pet food means you know what’s in it and where the ingredients came from.

Dear Dr. Fox:

Our 19-year-old terrier has many problems, and we need to know our options.

He is 80 percent blind and totally deaf. He recently started defecating on our rear deck, where his doghouse is.

We cannot let him in the house for more than a few minutes at a time because he will relieve himself on the carpet.

What makes the decision to put him to sleep a difficult one is that when he is allowed into the house, he behaves like a young pup. On these occasions, he is full of vigor and joy and, in his happiness, manages to run into objects.

He has many maladies and creates cleanup problems for his owners, but maintains a youthful vigor.

D.D., Medford, Ore.

D F: It is always a challenge, clinically and emotionally, to determine when it is time to consider euthanizing a beloved animal.

Your dog is suffering from being separated from you while outdoors, and the evident relief and playful joy when allowed in confirms this.

Try using doggy diapers, which many incontinent dogs readily accept. Take him for frequent walks so he can evacuate before you bring him indoors and put on a diaper.

He might need supplemental heat for the winter in his outdoor kennel, but, ideally, he should be brought to live his remaining life indoors, especially if he used to be an indoor pet.

Give this a try, and then, in better conscience, euthanasia could be considered after some time spent on indulgent, affectionate bonding and seeing if his quality of life improves.

Michael W. Fox, author of a newsletter and books on animal care, welfare and rights, is a veterinarian with doctoral degrees in medicine and animal behavior. Write to him at United Feature Syndicate, 1130 Walnut St., Kansas City, Mo. 64106.

2012 United Feature Syndicate