Rusty red black cat fur caused by defective pituitary gland?

Black care rusty red
Ziggy a black and white cat with rusty black fur. Photo copyright Julie.
Two useful tags. Click either to see the articles: Toxic to cats | Dangers to cats

A defective pituitary gland in a black cat may result in the cat’s hair becoming red/brown because of the lack of production a hormone produced by the pituitary gland. One of these hormones makes a certain protein (MCR1) in the cells of the cat’s skin work. This protein is employed in the conversion of pheomelanin (yellow/red) to eumelanin (brown/black) pigment. If it is not working the pigment stays yellow/red. Hence rusty coloured hair.

Note: this is my own work. No one has written this before. Please check. It took about 90 minutes of vigorous online research. This page is a follow up to “Is your black cat rusty red?” and Julie’s comments on that page.

Tabby Hair Srand
Tabby hair strand. This just illustrates the two types of pigment mentioned in this article.

Expanded Summary: The pituitary gland is situated at the base of the brain. It produces eight hormones. Decreased production of these hormones is called: Hypopituitarism.

There is a protein, MC1R, that is within the cell membrane of the skin, which is signalled (fired into action) by a “melanocyte-stimulating” hormone (MSH) that is released by the pituitary gland.

When activated by MSH, MC1R initiates the production of the brown or black pigment eumelanin from pheomelanin, which is a yellow-red color pigment and the precursor to eumelanin (brown black). In short, yellow and red pigment molecules are chemically altered to become brown and black.

MC1R is a protein that is the switch that converts yellow red to brown black. If it is not fired into action due to pituitary gland malfunction the pigment in the hair strands remain yellow/red and not brown/black.

One of the reasons for a malfunctioning pituitary gland is congenital – genetically inherited health problem. Other reasons (selected) are as follows:

  • Tumor
  • Brain injury
  • Infection
  • Stroke

Note: There is a connection between the “cure” for rusty red black cats, the supplement tyrosine, and the thyroid gland which in turn is affected by the pituitary gland:

One of the hormones produced by the pituitary gland is the thyroid-stimulating hormone (“TSH”). A deficiency of this hormone leads to hypothyroidism. Hypothyroidism is a lack of production of thyroxine (T4) and triiodothyronine (T3).  (Note: tyrosine is involved in the production of thyroid hormones).

Sources: these are numerous and include my own work and Wikipedia. The main work was about “connecting the dots”.

Please search using the search box at the top of the site. You are bound to find what you are looking for.

Useful tag. Click to see the articles: Cat behavior

14 thoughts on “Rusty red black cat fur caused by defective pituitary gland?”

  1. See how black, shiny black the rest of Katey is? All of them were that black in all light in years past. None of them are as rusty as Ziggy, yet, but I wonder if that’s where they’re heading. And I wonder if it’s a symptom of ill health, though these 3 are not exhibiting any other health abnormalities…

    1. Diane, thank you for showing me the pictures. Clearly, something strange is going on here. This is certainly not normal and it is common to all your cats. Something tells me that this may be very hard to diagnose. I think I know what I would do. I would firstly make sure that they are on different diets and secondly I would make sure that they live in different environments. The second objective will be hard to do. But there may be something in the environment which is affecting the cats. Has something changed in the environment? Have you put any new furnishings into your home over the past year?

      Although it is a long shot there may be something in the home that is giving off a chemical which is affecting them. That is a wild guess but I don’t think it is a bad guess.

  2. This is Spike, the one who’s been changing color the longest. It’s quite obvious around his shoulders.

  3. Hi, Michael. I came across your 2 blogs on this topic this week after taking my (formerly) 100% black cat to a vet for the first time since 2008. I’ve been noticing his color change over the past several years to a beautiful chocolate brown. He’s not completely brown or red (like Julie’s black/red & white cat), but it’s obvious he’s not completely black anymore. He also has lots of spots in his eyes, but is not ill in any way. He’s 12 years old.

    When we were seeing the vet, I commented on his color change, and, she immediately said it was a tyrosine deficiency. She also said the color change in his eyes is related to that, too. I went home to research this and that is how I found your comments on this topic. Her recommendation was to feed him a high quality kibble, which I don’t want to do. My cats eat ground, raw meat, bones & organs with commercial or homemade green supplements (very small amount each day). I am NOT a fan of kibble.

    This article puzzles me, now, because I have 4 cats, the 12-year-old, Spike, I spoke of above, a 13-year-old, Bobbie, who also is all black, and a 2.5-year-old, Katey, who is black and white. (The other cat is a 13-year-old, who is a very light tan & white tabby cat.) I just started noticing in the past few weeks, that Bobbie and Katey are also starting to turn. Whereas in the past their black was as black as black can be with no hint of brown or red (like Spike used to be), they both now show more of a brown color in certain light in some of their black.

    Spike and Bobbie might well be related, though different generations, I believe. I doubt Katey is related to them. They all found me over the years.

    It just doesn’t seem like they all 3 would have the same problem with their glands or hormones, etc., unless, their food is not complete, which I’ve been led to believe is. It’s what they’d eat in the wild, however, so it seems it SHOULD be complete.

    So, your statement in the other article, Is Your Black Cat Rusty Red?, that tyrosine deficiency causing color change in black cats is rare, may not be rare in my house.

    I’m wondering if you know if there are actual detrimental effects on a cat’s health with this tyrosine deficiency. Or is color change the ONLY symptom? I ask because my 4th cat, Bridgette, is a pretty sick little girl. She’s diabetic, and my holistic vet (not the same one Spike saw earlier this week) now thinks she may have Cushing’s Disease and/or Samoygi effect, based on her symptoms. This holistic vet never heard of the color change in black cats and tyrosine deficiency before. And, I figure, if 3 of my cats are deficient, the 4th one probably is, too. Could it, somehow, be related to her diabetes and suspected Cushing’s symptoms? Maybe Julie could shed some light on that if she knows anything there? Do you think I should begin supplementing her (and all the cats) with tyrosine to help curb her ravenous appetite? She’s developed quite a little pot belly because of it. I’ll clear it with my holistic vet, first.

    Sorry for the long post, but this seems SO applicable to all my kitties. Thank-you for any enlightenment you can give me!


    1. Two points come to mind (and I am not an expert on this problem). The first point is probably obvious. Black cats are really dark brown because the pigment in the fur strands, eumelanin is dark brown. When light shines through it, it looks light brown/rusty. The coat color depends on the light.

      Secondly, if the diet you are feeding to all three cats is deficient in tyrosine it would affect all the cats as you state — but you say it isn’t defecient in tyrosine. One other factor is age. Older black cats tend to go rusty. As to health a lack of tyrosine, I don’t think there are major or minor health issues. Lack of tyrosine is a symptom and the cause my be a serious health issue but a vet will answer that one.

      Cushings disease has been linked (in comments) to the rusty coat and lack of tyrosine but I forget where the comment is. You may have seen the comment. Sorry I am not very precise but this is a bit of a mystery.

      Thanks for posting Diane. Stick around. Do you have photos?

  4. Fascinating and along the lines of what I’ve been thinking but didn’t have the scientific understanding. Thank you! I’m amazed the docs haven’t been been interested but “rusting” wasn’t a good enough answer for me.

    Zig & his siblings were tossed over a fence prior to being weaned. Poor little babies. His siblings, two, were white and adopted out also. I only have a picture of his mom that shows she was a muted gray beauty with that Maine coat. The gray always intrigued me – it seemed a little unusual. Maybe she had the gene.

    Anyway, the info is fascinating and your attention & attention to detail is equally fascinating and appreciated.

    As for tyrosine … Been giving him 1/2 of the capsule mixed with a tiny bit of water & a few drops of diluted tuna juice. Slurp. One time per day but not with meals/protein because it would counter its absorption. Wondering if more is better … I don’t understand the quantity in the UC Davis study. Don’t want to give too much if it would be detrimental.

    Thank you. Thank you. Thank you, Michael.

    1. My pleasure. Of course it is just an exercise in trying to make connections and there is a connection.

      I think the problem is hormone based. You gave me that thought.

      Look, I don’t know if what I have written is the answer. It is just presenting some known facts in an way relevant to this problem and which appears not to have been presented before.

  5. Wow – interesting Michael. This kind of thing makes me seriously think you should write a book or something.

    Perhaps a website will suffice 🙂

    1. Thanks Marc. I was pleased with this. It was not easy. I had a inkling there was a connection and visited a large number of site before I found one. Julie, who lives with Ziggy, mentioned pancreatitis and that lead me to research the process of melanin and pheomelanin production and what might affect melanin production leaving pheomelanin.

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