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Why is my chihuahua losing hair, gaining weight, and always cold?

Updated on September 23rd, 2025

Pet's info: Dog | Chihuahua (Smooth Coat) | Male | neutered | 4 years and 2 months old | 6.2 lbs

my 4yr old chihuahua has symmetrical hair loss on trunk, very lethargic, always cold, and eye sight in dim rooms is getting worse. had a free T4ED done over a month ago and it came back at HIGH with 40.9. vet said it was normal and that chachi had CDA. put him on melatonin but hair keeps falling out..now on both shoulders in same pattern. he is in bed all day and all night except to eat and potty. he weighed 4.5 lbs until 6months ago...he now is 6.2lb and is eating less. please help us.

1 Answer

Most Helpful Answer

Stacey Anstaett, DVM

Answered By Stacey Anstaett, DVM

Veterinarian

Published on April 10th, 2019

It sounds like Chachi has a lot going on! What I am understanding Is that Chachi is lethargic (just lying in bed all day), he has gained about a pound and a half over the last 6 months despite eating less. He has symmetrical hair loss and is aways cold, and his vision in the dark is getting worse. You were told that the cause of the hair loss was CDA (color dilution alopecia). While this could cause the hair loss, CDA does not cause other symptoms in addition to hair loss; CDA does not explain the lethargy or weight gain. Melatonin has not helped his symptoms.
I am a little confused on his T4 results. Was a whole thyroid panel run, including a TSH? Were there any abnormalities on general bloodwork? (cbc and chemistry profile) All of this information can be helpful in piecing together what the problem is and how to best manage it. An abdominal ultrasound may also be recommended to more fully evaluate what may be causing the lethargy and weight gain.
It may be worth considering a consultation with an internal medicine specialist. Their advanced knowledge and experience managing complicated endocrine cases can be extremely helpful in cases that are difficult to manage. Find one near you here: https://find.vetspecialists.com
I am sorry that I don't have any specific answers or recommendations for you and Chachi, but I don't really have enough information to fathom a guess at what may be causing his issue. You can request an online consultation for a "back and forth" exchange of information that may be more beneficial to you.
Again, I encourage you to consider seeing a specialist with Chachi.

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