CONTRIBUTOR(S): Vetstream Ltd, Nicola Bates,
Estrogen toxicity in cats (HRT toxicity)
Estrogen toxicity in cats occurs when they are exposed to female sex hormones, either suddenly (acute exposure) or over a longer period (chronic exposure). The complications from this exposure vary depending on the dose and duration of exposure.
Example of a human HRT patch ©Vetstream Ltd
What is estrogen?
Estrogen is a hormone produced by the ovaries. Medicines containing estrogen compounds are used as contraceptives, hormone replacement therapies (HRT) or for other medical treatments. HRT patches, sprays and gels are commonly prescribed to support women through menopause and cats can be exposed to these products if they lick patches, sprays or gels, or when snuggling with owners.
What are the signs that my cat has been exposed to estrogen?
Some human estrogen products (patches, sprays and gels) are often designed to be absorbed through the skin and your cat’s skin can absorb the products in the same way as human skin, or cats may lick the product off their fur when grooming themselves. If your cat has a single exposure to these hormones (eg oral contraceptives), they are unlikely to display any symptoms. Very occasionally ingestion of an estrogen product may cause mild wobbliness and drowsiness, but these signs wear off without treatment. If your cat is regularly exposed to these hormones, from licking gels or from snuggling with someone near an applied HRT patch or recently applied gel then this chronic exposure could result in signs of toxicity such as a reduced appetite, more lethargic than usual, signs of estrus (coming into season – even if young or neutered), hair loss or enlarged mammary glands/nipples (even in male cats). Estrogen can also suppress bone marrow production which can be very serious, but it is very unlikely that cats would be exposed to high enough doses of human estrogen products for this to be problematic.
How do veterinarians diagnose this condition?
Your veterinarian will diagnose this condition primarily by reviewing your cat's history of possible hormone exposure and ruling out other conditions that could cause similar symptoms. It is important to tell your vet about any hormone medications in your home, even if you're not sure your cat has been exposed to them.
What is the treatment for estrogen toxicity?
The main treatment is identifying and removing the source of hormone exposure. Once exposure stops, most cats will gradually return to normal. However, if your cat is unwell your veterinarian may prescribe some supportive treatments to help them recover faster.
What is the expected outcome?
Most cats recover fully, though in cases of long-term exposure, it may take several months for all symptoms to disappear.
How can I prevent estrogen poisoning in my cat?
Keep medications safely out of your cat's reach. Store these items in sealed containers or in closed cabinets. Make sure to inform all family members and house guests about this hazard. Wash your hands after applying any HRT products and ensure that patches are covered by clothing and that gels have dried and the area is covered by clothing, before handling your cat. Dispose of used patches safely; they should be folded in half with the adhesive side inwards and discarded securely in the bin.
When should I contact my veterinarian?
Contact your veterinarian if you notice any unusual changes in your cat's behavior, eating habits, or physical appearance, especially if you have hormone medications in your home.