Endocrine & Nutritional Influences on the Skin

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Endocrinology of the Skin

There are various hormones that may influence the structure of the skin. These influences may be made apparent by the repeated long-term administration of various glucocorticoids or their analogues. Endogenous imbalances are generally seen in adult mature animals although congenital forms have been seen, especially with hypothyroidism. The hormones implicated as important for maintaining skin structure are thyroxine, cortisol and estradiol. Deficiencies or excessive production may result from abberations in the function of the hypothalamic-adrenal axis, the adrenal gland, thyroid gland and the gonads.

Cutaneous changes may include telogen hair follicles leading to alopecia, epidermal and dermal thinning, atrophy of sebaceous glands and the arrector pili muscles. There may also be an increased risk of microbial infection due to poor immune surveillance and delayed wound healing. There are significant differences between species in the manifestation of symptoms.

Nutrition and the Skin

Most animals are fed balanced diets and are therefore unlikely to exhibit symptoms when in veterinary care. There are some systemic conditions that can reflect deficiency as a result of hepatic or gut diseases for example.

Malnutrition whether due to a deficiency of protein or other nutrients or secondary to a debilitating condition may lead to a dull, brittle and thin haircoat and to dry, scaly skin. This in part reflects the high requirement for dietary amino acids to supply requisite building blocks for epidermal turnover and hair growth. Sulfur-containing amino acids are common in the skin and therefore sulfur supplementation is popular for dealing with skin conditions.

Trace Elements

Trace elements such as copper are rarely deficient in farm animals, although deficiency can be associated with poor fertility, ill-thrift and leukotrichia - leading to perioccular 'spectacles'. This reflects the role of copper in the formation of melanin.

Excessive exposure to trace elements can also have harmful effects and again, although rare, examples may include selenosis which is usually seen as alopecia in geographical areas with high selenium soil content for grazing animals.

Vitamins

• Vitamin A has a variety of roles that may infulence skin and coat condition. Some conditions may respond to supplementation with vitamin A or zinc, but this may not necessarily reflect a deficiency in the diet.

• Vitamin C deficiency may be associated with scurvy in guinea pigs. The impact of various disease processes that influence feed intake may lead to poor quality coat and skin condition.

• Vitamin D is processed in part in the skin.