Dr. Tom Shurlock speaks on Pituitary Health for horses:
The pituitary is a small gland nestling under the hypothalamus, the hind brain region. Under the control of the hypothalamus it is responsible for the release of a number of hormones or hormone releasing factors (these travel to other parts of the body and stimulate release from other organs). It consists of three parts which between them control the release, or production, of hormones for growth, energy metabolism, stress factors, reproduction/lactation and water balance.
Disorders of the pituitary manifest through a failure in the regulation of secretions. Giantism, hyperpituitarism, (including an overproduction of ACTH, leading to Cushing’s syndrome) hypothyroidism are all a result of pituitary malfunction, Cushing’s probably being the most familiar to horse owners – although any animal, and humans can suffer.
Alongside this there is another condition known as Equine Metabolic Disorder (EMD), which can be triggered by high circulating levels of glucose and insulin as in Insulin Resistance. This affects fat uptake into adipose tissue, releases the hormone Resistin which, in turn, reinforces Insulin Resistance. At the same time these fat cells, the adipocytes, release cortisol-like products, Adipokines, that convert cortisone to cortisol and cause a form of Cushings.
Both IR and EMD can result in overweight animals due to accelerated fat deposition, can stimulate amino acid intakes resulting in hairy animals, and impair glucose metabolism giving rise to lethargy and excessive thirst. It can be seen that some of these symptoms are also associated with Cushing’s. We can also see that the pituitary can also influence fat deposition and growth and therefore may well influence EMD & IR. So, although these major equine disorders may seem independent of each other they are intrinsically inter-related through dysfunction in hormone control.
In some circumstances we cannot influence the condition, for example a pituitary tumour, but we can possibly help mitigate the symptoms, or avoid the triggers that aggravate the disorders. Nutritionally we can help influence metabolic pathways and so hopefully bypass the triggers. At the same time, our increasing knowledge of nutraceuticals (“functional” plant components that have pharmaceutical-like effects) can help us understand how essential oils, flavonoids etc. may influence physiology.
Hormones and hormone releasing factors are ultimately dependent on internal and external factors and are generally released as a response to stimulation. Insulin, for example, is released when the pancreas secretes its digestive enzymes, and they are released by the action of gastric emptying. The hindbrain, in response to external influence, instructs the pituitary to release ACTH that stimulates the adrenal glands to release the “fright or flight” hormone adrenaline. In both these cases, when the mechanism that stops the stimulation does not kick in, IR & Cushing’s respectively may ensue. On the face of it nutritional manipulation does not seem relevant, but there is a common theme through which we can exert an influence.
Central to all biochemical pathways is the breakdown of sugars to produce energy. These sugars are supplied in the diet as starch, from cereals, tubers oilseeds and legumes, sugars and fructans from grass, sugars from roots and lactose from milk. They are enzymatically broken down in the small intestine and absorbed, where they undergo a process called glycolysis and the TCA cycle . This is a metabolic pathway generating energy, but is a pathway that also interconnects with other processes such as fat generation.
Metabolic processes are driven on a “supply and demand basis”; that is if there is, for example, more sugar than the body needs for energy production it is converted firstly to glycogen (a first reserve for changing back to glucose) and secondly to long term storage as fat. In the case of compromised animals we have to redefine how much sugar is too much.
Any reduction in sugar absorption will improve the situation. Less sugar, less insulin, less fat deposition more protein metabolism and so the symptoms mentioned previously begin to reduce. The trouble is there is a lot of sugar (or starch, or fructose) out there. It’s our fault. We’ve been breeding plants to increase their yields for generations, but the horse’s metabolism has stayed the same. The grass he evolved alongside on the Russian steppes bears little resemblance to the high protein, high sugar leys we grow now and we have to look further afield to find low sugar alternatives. There are alternatives out there but at the same time as reducing sugar (and fat – too much fat goes straight to those adipocytes) we are making our horses do more, so we want to maintain energy intake.
One answer is the use of super-fibres. Beet pulp and lucerne fibre have high degradability and are fermented to produce a profile of volatile fatty acids that, when absorbed, can enter the energy metabolism cycle at various points without stimulating insulin release and minimizing fat deposition. By reducing sugar intake and manipulating VFA profiles with super-fibres we can move away from the cycle of fat deposition, cortisol production and hormonal imbalances. In addition, as beet fibre has a proven prebiotic effect we can get more from out forages and potentially feed lower quality (i.e. low sugar) hays and chaffs to further reduce impacts on hormone dysfunction.
Speedi-Beet (100% Beet pulp with a sugar content of less than 5%) and Fibre-Beet (Beet pulp and Lucerne) are two such super-fibres.
As mentioned before many major metabolic pathways interact with Glycolysis and TCA. Amino acids are broken down, as are fats and their components enter the cycle. Some amino acids are transformed into others and so can be recycled; and excess nutrients can be converted into fat. Metabolism is controlled through hormones by requires many trace elements to act as cofactors in the biochemistry. Essential fatty acids, omega-3 and phospholipids have structural rather than storage capabilities and essential amino acids are needed to ensure protein regeneration occurs without imbalance that can lead to excessive metabolism. Although supplying a sugar low diet is essential for compromised animals a preparation that addresses all these issues, especially at the hormone imbalance/laminitis interface is equally important.
The nutritional emphasis is to reduce the impact on hormone dysfunction by modifying the metabolic pathways influenced. However it may be possible to modulate the hormones directly, to help reduce excessive output, which is the root cause in above conditions; and it’s here we can turn to nutraceuticals.
The chasteberry (Vitex agnus-castus) has been the subject of much research into its effect in interacting with hormone production. It has been shown that the essential oils of Vitex can stimulate thyroid C cell activity, reduces adrenal gland weight, affect vasomotor activity and may have androgenic and progesteronic (reproductive) effects (data on file). The common factor for these differing observations are the hormone and hormone releasing factors of the pituitary gland.
Evitex, a source of chasteberry, is a product that can support pituitary function, not only for reproductive health but maybe also for energy metabolism conditions.
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Copyright 2016 Emerald Valley Natural Health, Inc
Informative article and interesting.