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Home:Equine Diseases:Hormonal Problems

Equine Diseases


When we talk about equine hormonal problems or equine hormonal imbalances, it is mainly mares we are talking about although hormonal imbalances have been associated with poor fertility in stallions. Hormones are chemical substances created by the body and control numerous bodily functions.

Very briefly and to give a simple overall layman's view of what the equine hormones do, the main hormones which can become imbalanced or cause problems are:

  • The Gonadotropin Releasing Hormone (GnRH) this plays a major part in the regulation of the reproductive system.
  • Follicle stimulating hormone (FSH) - produced in the pituitary gland and responsible for the stimulation of follicle development.
  • Estrogens – they convey female characteristics and control fertilization.
  • Estradiol – the principal estrogen produced by the ovary and active in the pregnant mare
  • P rogesterone - prepares the uterus to receive and sustain the fertilised egg. Prostaglandin – causes uterine contractions
  • Inhibin - male feedback hormone made in the testicles to regulate FSH production by the pituitary gland
  • Recombinant equine growth hormone – associated with muscle definition, body condition, wound healing, growth and regulation of metabolism


Some of the symptoms you may notice which could indicate equine hormonal problems are:

  • disruptive behaviour – known as “marish behaviour”
  • poor performance,
  • reduced movement,
  • hypersensitivity to being touched
  • becoming cold-backed (displaying symptoms of painful back – e.g. dipping away from the saddle)
  • mood swings - even the most even-tempered mare can become unpredictable and aggressive.
  • shortened strides
  • irritability
  • colic
  • change in appetite
  • repeated urination
  • changes in overall body condition,
  • changes in hair growth
  • change in energy levels
  • poor fertility in stallions


Possible causes put forward for Equine hormonal problems:

•  Onset of “the season” – this is the "heat" stage of the cycle when the mare is receptive to the stallion's advances

•  Cushing's disease

•  Improperly spaced vaccinations

•  Stress


Consult your vet and ask for

•  a full health check

•  a rectal examination of your mare's reproductive system

•  an ultrasound scan of her ovaries.

•  blood tests to detect equine hormonal levels

You will then have a full picture and can work out a treatment programme depending on what is expected of your horse. For example, if your horse is a high performance animal and competitive activity dictated by the calendar is a large part of its life, the treatment will be more important than if your horse is a pet and you can afford to let it have “off days” and rest without it causing inconvenience.

The most common treatments for equine hormonal problems are herbal or food supplements.

Herbal mixtures span a wide range from Chaste Berry (also known as Agnus Castus) Chamomile, Glycyrrhiza, Melissa,Verbena , Passion flowers, Lemon Balm, Raspberry Leaf, Dong Quai root, Licorice root, Red Clover, Black Cohosh, powdered Wild Yam, Valerian root, Vervain, Passiflora and Hops. They can be stand alone or in combination form. It is difficult to know which herbs will suit your horse so you will need to research these various herbs and their effects and try to get a combination which best suits your horse's particular hormonal problems. You may have to try many of the herbs over time to see which suits best. The Chaste Berry in particular, is considered very effective as it is thought to act on the pituitary gland to suppress seasonal activity. You may even consider it worth your while to make your own mixtures.

Food supplements tend to be a combination of anti-oxidants, glutathione, vitamins, minerals, carotenoids, bioflavanoids and trace elements chosen to support equine hormone regulation.

Check your choices with your vet and ask for his/her recommendations. The manufacturers of the various food and herbal mixtures will also be a great source of information and help. There are many endorsements on line which should be of benefit to you in making your decisions.

Herbal supplements for equine hormonal problems should be stopped during the winter months and resume again in the Spring.

Equine hormonal additives is another form of treatment but many are far from ideal and are not suitable for long term use. Some products contain substances banned under FEI or Jockey Club rules. Depending on the work your horse is expected to do, you will need to ensure that any product you use complies with regulations.

One of the most effective treatments is to prevent “seasons”. This will have the double effect of avoiding the hormonal as well as the physical fall-out. It mostly takes the form of the “equine pill” so you need to discuss this method with your vet. There are other developments being perfected in the form of vaccines but these will only be of help in the future.

A low dose of phenylbutazone (bute) around the time of “the season” can reduce pain and inflammation, but again, this is unsuitable for mares if competing under FEI or Jockey Club rules.

If you have time and if your horse is a very special part of your life , alternative therapies such as those listed below are very much worth looking into. Every horse deserves this level of attention to help it cope with being so far removed from its ancient roots.

•  Equine Shiatsu -gentle therapy combining acupressure & massage techniques

•  Reiki - t his particularly applies to horses as they are far more in tune with themselves and their environment than people. Energy is drawn to the area requiring healing in exactly the right quantity and at exactly the right frequency. The body then heals itself

•  Aromatherapy - through the use of various oils this is considered an effective and gentle answer to many of today's common animal problems, often bringing relief where allopathic medicines hold no answer.

•  Acupuncture - Stimulation of specific points on the body by small needles to regulate various biological functions and help the body heal itself .

- Animal Communication Telepathy – recognised as a means of bridging the gap of understanding between people and animals to cultivate healing, understanding and growth giving a greater understanding of our animal companions.