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Equine Internal Medicine Q&A 21 (view source)
Revision as of 08:47, 1 June 2011
, 08:47, 1 June 2011Created page with "{{Template:Manson Mair}} centre|500px<br> <br /> '''You are asked to examine an 18-year-old Warmblood gelding that has developed ..."
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[[Image:Equine Internal Medicine Q&A 20.jpg|centre|500px]]<br>
<br />
'''You are asked to examine an 18-year-old Warmblood gelding that has developed progressive alopecia, which started in the neck region. Haematological evaluation reveals a haematocrit of 30% (n = 36–42%) and a normal leucocyte count (8.9x109/l with 21% lymphocytes, 1% eosinophils and 78% neutrophils). The total serum protein concentration is normal (81g/l with 31.7% albumin, 14.3% alpha-globulins, 29.4% beta-globulins and 24.6% gamma-globulins). Basal T4 concentration is low.'''
<br />
<FlashCard questions="4">
|q1=What is the most likely endocrinopathy to cause these lesions?
|a1=Hypothyroidism. Thyroid dysfunction is rare in the horse. Equine hypothyroidism can be classified into four groups:
#hypothyroidism in foals;
#hypothyroidism in adult horses;
#euthyroid sick syndrome; and
#thyroid neoplasia. <br><br>
Hypothyroidism in foals is usually associated with prognathism, ruptured tendons, forelimb contracture, delayed ossification of the carpal and tarsal bones, and goitre. The prognosis is extremely poor. <br><br>
The clinical signs of hypothyroidism in adult horses are cessation of growth, hypothermia, lethargy, irregular areas of alopecia and thickened face.
|l1=
|q2=Which three thyroid hormones can you name, and how are they controlled?
|a2=
Thyroglobulin is the prohormone of the thyroid hormones
*thyroxine (T4),
*tri-iodothyronine (T3) and
*reverse triiodothyronine (rT3). <br>
Once released into the circulation, the hormones are rapidly bound to plasma proteins and only 0.2% T3 and 0.06% T4 is free or unbound. Only the free forms are biologically active.<br><br>
Thyroid-releasing hormone (TRH) is released from the hypothalamus in response to decreased free T4, which in turn stimulates the anterior pituitary to release thyroid-stimulating hormone (TSH). <br><br>
There is a slight diurnal variation in thyroid hormone concentrations with low concentrations during the night. <br><br>
Thyroid hormones regulate cell growth and differentiation, and regulate energy metabolism.
|l2=
|q3=Does diet influence the plasma concentrations of these hormones?
|a3=
*In weanling foals fed a diet in accordance to their energy and protein demands, both serum T4 and T3 concentrations increase within two hours of feeding.
*Undernutrition in foals results in an increase in T4 concentration, but T3 concentration remains unchanged.
*On the other hand, excess energy and protein in foals result in a decreased T4 concentration and an increased T3 concentration. <br><br>
*In adult horses, food restriction induces a decrease in thyroid hormones.
*In addition, non-thyroidal factors affect thyroid function in horses.
*Three of these factors,
#age,
#pregnancy and
#low temperature, <br>
:are associated with increased levels of thyroid hormones. <br><br>
*Thyroid hormone concentrations in normal foals are up to 14 times higher compared with those of horses older than two years.
*Serum thyroid hormone concentrations are decreased following concurrent disease and the administration of phenylbutazone (T4 only).
*However, the administration of dexamethasone does not change baseline T3 and T4 concentrations.
|l3=
|q4=What is the euthyroid sick syndrome?
|a4=
*The euthyroid sick syndrome occurs in horses.
*Disease unrelated to thyroid disease can depress basal thyroid hormone levels as a normal response to minimize the catabolic effects of thyroid hormone during disease.
*In cases of euthyroid sick syndrome, low baseline T3 and T4 concentrations respond normally to TSH administration.
|l4=
</FlashCard>
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[[Category:Equine Internal Medicine Q&A]]
[[Image:Equine Internal Medicine Q&A 20.jpg|centre|500px]]<br>
<br />
'''You are asked to examine an 18-year-old Warmblood gelding that has developed progressive alopecia, which started in the neck region. Haematological evaluation reveals a haematocrit of 30% (n = 36–42%) and a normal leucocyte count (8.9x109/l with 21% lymphocytes, 1% eosinophils and 78% neutrophils). The total serum protein concentration is normal (81g/l with 31.7% albumin, 14.3% alpha-globulins, 29.4% beta-globulins and 24.6% gamma-globulins). Basal T4 concentration is low.'''
<br />
<FlashCard questions="4">
|q1=What is the most likely endocrinopathy to cause these lesions?
|a1=Hypothyroidism. Thyroid dysfunction is rare in the horse. Equine hypothyroidism can be classified into four groups:
#hypothyroidism in foals;
#hypothyroidism in adult horses;
#euthyroid sick syndrome; and
#thyroid neoplasia. <br><br>
Hypothyroidism in foals is usually associated with prognathism, ruptured tendons, forelimb contracture, delayed ossification of the carpal and tarsal bones, and goitre. The prognosis is extremely poor. <br><br>
The clinical signs of hypothyroidism in adult horses are cessation of growth, hypothermia, lethargy, irregular areas of alopecia and thickened face.
|l1=
|q2=Which three thyroid hormones can you name, and how are they controlled?
|a2=
Thyroglobulin is the prohormone of the thyroid hormones
*thyroxine (T4),
*tri-iodothyronine (T3) and
*reverse triiodothyronine (rT3). <br>
Once released into the circulation, the hormones are rapidly bound to plasma proteins and only 0.2% T3 and 0.06% T4 is free or unbound. Only the free forms are biologically active.<br><br>
Thyroid-releasing hormone (TRH) is released from the hypothalamus in response to decreased free T4, which in turn stimulates the anterior pituitary to release thyroid-stimulating hormone (TSH). <br><br>
There is a slight diurnal variation in thyroid hormone concentrations with low concentrations during the night. <br><br>
Thyroid hormones regulate cell growth and differentiation, and regulate energy metabolism.
|l2=
|q3=Does diet influence the plasma concentrations of these hormones?
|a3=
*In weanling foals fed a diet in accordance to their energy and protein demands, both serum T4 and T3 concentrations increase within two hours of feeding.
*Undernutrition in foals results in an increase in T4 concentration, but T3 concentration remains unchanged.
*On the other hand, excess energy and protein in foals result in a decreased T4 concentration and an increased T3 concentration. <br><br>
*In adult horses, food restriction induces a decrease in thyroid hormones.
*In addition, non-thyroidal factors affect thyroid function in horses.
*Three of these factors,
#age,
#pregnancy and
#low temperature, <br>
:are associated with increased levels of thyroid hormones. <br><br>
*Thyroid hormone concentrations in normal foals are up to 14 times higher compared with those of horses older than two years.
*Serum thyroid hormone concentrations are decreased following concurrent disease and the administration of phenylbutazone (T4 only).
*However, the administration of dexamethasone does not change baseline T3 and T4 concentrations.
|l3=
|q4=What is the euthyroid sick syndrome?
|a4=
*The euthyroid sick syndrome occurs in horses.
*Disease unrelated to thyroid disease can depress basal thyroid hormone levels as a normal response to minimize the catabolic effects of thyroid hormone during disease.
*In cases of euthyroid sick syndrome, low baseline T3 and T4 concentrations respond normally to TSH administration.
|l4=
</FlashCard>
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