Can Hormones Cause Hair Loss in Dogs?

In a young, unspayed female dog suffering from hair loss, hormones could be to blame.


Dr. Barchas,

I have a 15-month-old female Chihuahua. She is tan in color, but over the past few months she has gotten darker on her lower sides, legs, and around her ear.

My vet did a skin scraping in two areas, and as necessary scraped until the skin was raw. She did not see any mites, but didn’t think she would because the hair loss (skin darkening) is so symmetrical. She thought it could be hormonal as the dog has not been spayed; she also stated it could be her thyroid but did not think it would be, as the dog is not exhibiting any other signs of hypothyroidism. She also didn’t think it was allergies.

The dog eats (and loves) Blue Buffalo’s life protection formula. Do you have any ideas? Should we just watch it?


Demodectic mange, also known as puppy mange, is triggered by a ubiquitous organism in the genus Demodex. The organism is a mite, and by ubiquitous I mean that virtually every dog on earth has been exposed to it.

Adult dogs with mature and fully functioning immune systems suppress the mite and do not show symptoms. However, young dogs (less than two years old) and adult dogs with compromised immune systems may develop demodectic mange.

Symptoms include patchy hair loss with occasional secondary bacterial skin infection, which usually resolves without treatment. More serious symptoms occur less frequently (although some breeds such as Pit Bulls are predisposed). The more serious form causes hair loss over large portions of the body, which generally require treatment, often for several months.

Demodectic mange is diagnosed with a test called skin scraping. It’s not rocket science: the skin is scraped with a scalpel blade to collect tissue in an attempt to harvest mites. The collected tissue is viewed under a microscope, and if mites are seen the diagnosis is made. Demodectic mange generally does not cause skin discoloration unless a significant secondary bacterial or yeast infection is present. It is more likely to cause random patches of hair loss, not symmetrical ones. Skin scraping tests in dogs with active demodectic mange have a pretty high yield.

James, although your dog is the right age for demodectic mange, none of the other features of her skin condition are consistent with the syndrome. They are, however, consistent with hormonal issues or (as vets call them, endocrinopathies) that cause symmetrical hair loss, often with skin discoloration.

Hypothyroidism is one of them, but it is vanishingly uncommon in young dogs. However, sex-hormone-related hair loss is very common at your dog’s age. She is newly sexually mature, and her estrus (heat) cycles are ramping up. All kinds of hormonal changes are going on in her body, and it is very likely that the hair loss is related to them.

Here is my question: Why have you not spayed your dog?

I recommend against breeding her, since she has a likely endocrine issue. If you breed her and sell puppies who later develop this issue (which may well have a hereditary component), you could end up in a bunch of trouble with your customers. A very small minority of people do not spay their dogs because they have found some studies that indicate not spaying can lead to increased longevity. This is unlikely to be the case in your dog, since she is showing physical symptoms of a probable endocrine issue.

Since it would be irresponsible to breed your dog, and since your dog is unlikely to derive any health benefits from being intact, the simplest solution to this situation is to spay her. There’s a very significant chance that the skin issues will resolve after that.

If you choose not to spay her, I do not recommend merely watching the situation. Instead, follow up with a dermatologist or internal medicine specialist for assessment and (probable) hormone assays to determine what precisely is going on and what can be done.

Got a question for Dr. Barchas? Ask our vet in the comments below and you might be featured in an upcoming column. (Note that if you have an emergency situation, please see your own vet immediately!)

4 thoughts on “Can Hormones Cause Hair Loss in Dogs?”

  1. My golden retriever is 18 mths old .
    Only had one season at 14 mths old. Suddenly she has started loosing a load of hair on her back end. And her coat has become so dull .
    She has gone really dark pigmentation all over her tummy .
    But she fit has a appetite.
    Please help

  2. My 9 year old poodle has lost most of her hair she is in heat all the time I am wondering if she could have a hormone in balance
    Please help

  3. Dr. Barchas,
    We have a black lab born april 4, 2016. Over the past 1.5-2 months, she has been losing her hair….mostly on tummy, now chest area, thinning out all over. Been checked for mites…Thyroid test came back negative….currently getting her hormones checked. She hasn’t been spayed and came into heat at approximately 9 months, nothing since. Please advise what could be causing her to lose her hair. Thanks Ingrid

    1. Hi there Ingrid,

      Thanks for reaching out! You can contact Dr. Barchas directly through his website here:

Leave a Comment

Your email address will not be published. Required fields are marked *

Get Dogster in your inbox!

Stay informed! Get tips and exclusive deals.

Let Dogster answer all of your most baffling canine questions!

Starting at just

This error message is only visible to WordPress admins
There has been a problem with your Instagram Feed.


Follow Us

Shopping Cart