Term
| What is the structure of the thyroid gland? |
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Definition
| The thyroid gland is enclosed in a fascia (outer, middle and inner). The inner layer forms a true capsule, extensions of this capsule into the gland form septae which divide the gland into lobes and lobules. Lobules are composed of follicles which are the structural unit. The follicles consist of areas of colloid (circular) enclosed by epithelial cells. The pithelial (or follicular) cells produce tertradothronine (T4) and tri-iodothryronine (T3) |
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Term
| Explain roughly how T3 and T4 are made |
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Definition
| Thyroglobulin is maded by the folliclaur cell andis secreted into the colloid by exocytosis. It then binds to iodine (that comes from the blood, through the follicular cell and into the colloid) to make monoiodotyrosine, or MIT. MIT then binds to another iodine to form di-iodotyrosine (or DIT). These then get glued together to form T3 (MIT+DIT) and T4 (DIT+DIT) |
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Term
| Which thyroid hormone is thyroxine? |
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Definition
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Term
| Does T3 or T4 have a greater metabolic activity? |
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Definition
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Term
| What is the primary activity of thyroid hormones? |
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Definition
| To increase basal metabolic rate |
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Term
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Definition
| Increase in carb and fat metabolism |
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Term
| What are some of the actions of T3? |
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Definition
Foetal organ maturation and differentation
Growth
Control of BMR
Heart rate and myocardial contractility |
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Term
| Do cats get hypo or hyper throidism? |
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Definition
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Term
| Do dogs get hypo or hyper thyroidism? |
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Definition
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Term
| Does idoine deficiency or excess cause goitre? |
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Definition
| Ha! Trick question! BOTH DO! |
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Term
| What are the causes of goitre? |
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Definition
Enlargment of the thyroid gland due to hyperplasia or hypertrophy
Caused by iodine deficiency or excess
Ingestion of goitrogenic substances (such as Brassoca and sulponimides)
It may also be hereditary |
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Term
| What are the main causes of hyperthyroidism in dogs? |
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Definition
| Lymphocytic thyroidits, body attacks the T3 and T4 hormones |
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Term
| What are the clinical sings of hypothyroid disease? |
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Definition
Lethargy
Heat seeking
Obesity
Alopaecia
Bradycardia |
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Term
| What is the clinical pathology of hypothyroidism? |
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Definition
Anaemia - mild, normochromic and normocytic (occurs in 25% of dogs)
Increased blood cholesterol (33-75% cases)>12mmol/L is suggestive of hypoT |
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Term
| What are some tests of thyroid function? |
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Definition
TSH stimulation test
Assay of endognous TSH
Assay of TT4 and TT3
Assay of FT4 and FT3
Total T3 and T4 is more diagnostically sensitve |
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Term
| What are some of the draw backs of TSH stim test? |
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Definition
| Expensive and difficult to obtain TSH, and can cause anaphalixis |
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Term
| What is Euthyroid Sick Syndrome? |
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Definition
| Abnormal levels of T3, T4 etc, without a thyroid illness, so te thyroid is fine the odd levels are being caused by something out side of the thyroid |
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Term
| If you test a dog for TT4 and the levels are low, what can be the cause? |
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Definition
Primary hypoT
Non-thyroidal illness (Diabetes, renal failure)
Iatrogenic
Some dogs (Gaze hounds) have a lower level
Secondary hypoT (rare)
Iodine deficiency (also rare) |
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Term
| What can cause feline hypoT? |
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Definition
| Iatrogenic - post thyroid surgery in hyperT cats |
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Term
| What are some clinical signs of hyperT in cats? |
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Definition
| Wieght loss, palpable thyroid, thin, hyperactivity, polyphagia, tachcardia |
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Term
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Definition
Mildly elevated PCV
Mild to moderate elevation of liver enzymes |
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Term
| What can you do to test for hyperT? |
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Definition
Measure TT4 or FT4. There may be fluctuations, but in hyperT animals, it will be consistently above the ref range
Can also do a T3 supression test |
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Term
| What is he main function of the parathyroid gland? |
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Definition
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Term
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Definition
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Term
| What does parathyroid hormone do? |
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Definition
It is stimulated in response to a decrease in serum Ca, causing Ca to be released from the bone, increase of absorbtion from the GIT and reabsorbtion by the kidneys.
The net result is an increase in Ca and a decrease in Pi |
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Term
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Definition
| Produced by the thyroid cells in response to high Ca, and causes inhibition of PTH action on the bone and increase excretion of P by the kidneys. the net result is a decrease in P and Ca |
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Term
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Definition
Viamin D
Formed in the kidneys under the influence of PTH and promoted Ca and phos abs from the GIT
It is long term Ca control |
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Term
| How is Ca transported in the blood? |
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Definition
| 50% as free Ca and 50% bound (45% albumin and 5% other anions) |
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Term
| What are some clinical signs associated with hyperparathyroidism? |
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Definition
| Extensive reabsorbtion of bone with proliferation of firous tissues, poorly mineralised immature bone, PU/PD, muscle weakness |
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Term
| What can cause hyperparathyroidsim? |
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Definition
| Tyroid adenoma (canine, rare), renal dysfunction, nutritional fuck ups |
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Term
| What can cause hypercalcaemia? |
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Definition
Increased albumin
Neoplasia (anal sac adenocarcinoma, lymphoma other neoplasia (rarer))
hyperparatyroidism |
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Term
| How does pH affect [Ca ions]? |
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Definition
| H ions displace the Ca on the albumin |
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Term
| How should you investigate hypercalcaemia? |
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Definition
If ou have a patient come in with a persitantly high tCa, look at the albumin. If albumin is high, then also check the fCa
Next rule out hypercal as a result of melignacy (rectal exam and a thoruough physical), cbc biochem, urinalysis,xrays
Rule out chronic renal failure
Then test for HyperPT |
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Term
| What is the effect of a decrease in albumin? |
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Definition
| The free (bioactive) Ca will remain the same, but total Ca will be down |
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Term
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Definition
Decreased albumin
Decreased PTH
Oxaate posioning
Increased urinary excretion (ethylene glycol posioning)
Acute pancratitis |
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Term
| What are some clinical signs of hypocal? |
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Definition
| Increased neuromuscular excitability, flaccid paresis/parylisis |
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