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| | Results from a cycle of hyperplasia and hypoplasia. | | Results from a cycle of hyperplasia and hypoplasia. |
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| − | ==Hypothyroidism== | + | ==[[Hypothyroidism]]== |
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| − | The most commonly described endocrinopathy in the dog. Multiple possible aetiologies, including:
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| − | *'''Primary''' hypothyroidism:
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| − | **Congenital: '''Cretinism''', rare.
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| − | **Acquired: E.g. Neoplasia. Represents 90% cases.
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| − | *'''Secondary''' hypothyroidism: Pituitary dysfunction ,10% cases.
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| − | *'''Tertiary''' hypothyroidism: Hypothalamic dysfunction, rare.
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| − | *Miscellaneous E.g. iodine deficiency, rare.
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| − | ''Clinical signs'':
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| − | *Lethargy
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| − | *Obesity
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| − | *Intolerance to cold
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| − | *Bradycardia
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| − | *Bilaterally symmetric, non-pruritic alopecia
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| − | *Occasional neurological signs with neoplasia
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| − | ===Cretinism===
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| − | Affected animals are '''disproportionate dwarfs''' with broad skull, heavy legs and an ataxic gait. Thyroid hormones are needed for normal osteogenesis and endochondral ossification. Also see myxoedema (deposition of mucoid material in the skin giving a '''tragic facial expression''').
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| − | ===Lymphocytic thyroiditis===
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| − | [[Image:Autoimmune thyroiditis.jpg|right|thumb|125px|<small><center>'''Lymphocytic thyroiditis'''. Courtesy of A. Jefferies</center></small>]] | |
| − | Causes primary hypothyroidism in the adult. Exact aetiology unknown but thought to be an autoimmune disease. Thyroid has an infiltrate of lymphocytes. See fibrous replacement of thyroid tissue which progresses to complete destruction. Clinical signs are not seen until 75% of the functional tissue of the thyroid is lost.
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| − | Similar disease to '''Hashimotos thyroiditis''' in humans.
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| − | Primary hypothyroidism in the adult animal may also be due to;
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| − | [[Image:Thyroid carcinoma.jpg|right|thumb|125px|<small><center>'''Thyroid carcinoma'''. Courtesy of A. Jefferies</center></small>]]
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| − | *Neoplasia
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| − | *[[Thyroid Gland - Pathology#Goitre|Goitre]]
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| − | *Atrophy
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| | ==Hyperthyroidism== | | ==Hyperthyroidism== |