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”.

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…

    • 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.


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