Thy­roid dis­ease is a rel­a­tive­ly com­mon prob­lem in dogs. While it is usu­al­ly treat­able, learn­ing that your dog has a thy­roid con­di­tion is un­der­stand­ably con­cern­ing.

The thy­roid is a but­ter­fly-shaped gland that is lo­cat­ed on both sides of a dog’s neck. It pro­duces the hor­mone thy­rox­ine (T4), along with sev­er­al oth­er im­por­tant thy­roid hor­mones. These hor­mones play a large role in a dog’s me­tab­o­lism and can cause ma­jor prob­lems when they are not pro­duced at nor­mal lev­els. A dog’s body tem­per­a­ture, heart rate, and food util­i­sa­tion are all af­fect­ed by the lev­el of thy­roid hor­mone in the blood­stream.

Hy­per­thy­roidism oc­curs when the thy­roid gland is over­stim­u­lat­ed caus­ing large amounts of thy­roid hor­mones to be pro­duced and re­leased in­to the body, re­sult­ing in a con­stant state of meta­bol­ic hy­per­ac­tiv­i­ty.  This dis­ease is rare in dogs and is much more com­mon in cats, but when it does af­fect dogs, it is usu­al­ly se­ri­ous.

The most com­mon cause of hy­per­thy­roidism in dogs is a type of can­cer, called thy­roid car­ci­no­ma, which trig­gers an ex­ces­sive pro­duc­tion of the hor­mone thy­rox­ine. The tu­mour, found on the neck close to the thy­roid gland, in­ter­feres with the nor­mal func­tions of the thy­roid. In some cas­es of hy­per­thy­roidism, the over­pro­duc­tion of thy­roid hor­mones does not orig­i­nate in the thy­roid it­self, but oc­curs as a re­sult of over­med­ica­tion with thy­roid sup­ple­ments when a dog has hy­pothy­roidism (un­der­ac­tive thy­roid).

Dogs that con­sume com­mer­cial raw meat di­ets con­t­a­m­i­nat­ed with thy­roid tis­sue can al­so de­vel­op hy­per­thy­roidism, so you should al­ways con­sult your vet be­fore switch­ing your dog to a raw food di­et. Sup­ple­ments that con­tain kelp or sea­weed can trig­ger hy­per­thy­roidism if in­gest­ed. Any breed of dog is sus­cep­ti­ble to get­ting hy­per­thy­roidism. How­ev­er, the dog breeds that have a high­er in­ci­dence of de­vel­op­ing a thy­roid tu­mour are Bea­gles, Box­ers, Gold­en Re­triev­ers, and Siber­ian Huskies. Hy­per­thy­roidism oc­curs most of­ten in old­er dogs.

The symp­toms of hy­per­thy­roidism in dogs in­clude:

• Weight loss de­spite no change (or even an in­crease) in ap­petite

• Hy­per­ac­tiv­i­ty

• In­creased ap­petite

• In­creased thirst

• In­creased uri­na­tion

• En­large­ment of thy­roid gland

• Vom­it­ing

• Di­ar­rhoea

• In­creased amount of stool

• Con­ges­tive heart fail­ure

• Tachy­car­dia (fast heart rate)

• Heart mur­murs

• Car­diomegaly (en­larged heart)

• Dys­p­nea (short­ness of breath)

Hy­per­thy­roidism can be di­ag­nosed eas­i­ly with a spe­cialised blood test that mea­sures thy­roid hor­mones.

Var­i­ous op­tions are avail­able for treat­ing hy­per­thy­roidism in dogs, de­pend­ing on the cause of the hy­per­thy­roidism. If a tu­mour is the cause, there are sev­er­al op­tions to treat it, such as surgery, ra­di­a­tion, and chemother­a­py. Your vet will de­ter­mine the best course of ac­tion. If di­et or a sup­ple­ment is the cause of the hy­per­thy­roidism, dis­con­tin­u­ing these will re­solve the con­di­tion. De­creas­ing the dosage of the thy­roid sup­ple­ment for hy­pothy­roid dogs that are over­med­icat­ed will re­solve the hy­per­thy­roid symp­toms.

To help pre­vent hy­per­thy­roidism in dogs, a healthy di­et is im­por­tant. If you feed your dog a raw di­et, be aware that cer­tain in­gre­di­ents such as gul­lets, an­i­mal necks, and head meat con­tain high­er amounts of thy­roid hor­mones, which can trig­ger hy­per­thy­roidism. If your dog has been di­ag­nosed with hy­pothy­roidism, keep in mind that ad­min­is­ter­ing a high dose of med­ica­tion can have the same ef­fect on a dog’s body as an over­ac­tive thy­roid gland. Be aware of any symp­toms re­lat­ed to hy­per­thy­roidism, and con­sult your vet im­me­di­ate­ly if you no­tice any of them. Your vet will help you cor­rect the med­ica­tion dosage.

Hy­per­thy­roidism in dogs is un­com­mon, but if you are see­ing signs and symp­toms, get your dog checked out im­me­di­ate­ly.