Week 6- thyroid disorders Flashcards
What is lymphocytic thyroiditis?
- Thyroid infiltrated by inflammatory cells
- Clinical signs when over 80% of thyroid tissue is destroyed
- TgAA is detectable until endstage destruction
What is idiopathic atrophy of the thyroid gland?
- Progressive reduction in size of the thyroid follicles + replacement with adipose tissue
- still unsure why it occurs
What is neoplastic destruction?
- thyroid tumour from elsewhere
- but 80% of tissue destruction is needed to cause clinical hypo T4
What is the signalment and clinical signs of hypothyroidism?
- Middle-aged to older dogs
slowing down of all organ systems
What would be the expected haemotology findings with hypothyroidism?
- Normocytic, normochromic, mild non-regenerative anaemia- due to decreased RBC production
What would be the expected Biochemistry findings with hypothyrodism?
- Fasting hypercholesteraemia due to increased lipid metabolism (synthesis and degredation)
- Mild to moderate increase in ALT and ALKP
What would you expect the total T4 to look like with hypothyroidism?
highly sensitive test
- If normal T4- disease is unlikely
- must be interpreted in conjunction with TSH
What is the main risk of doing a TSH test?
Risk of false negatives
What is euthyroid sick syndrome?
non-thyroidal illness supressing concentration of circulating thyroid hormones
What are the two additional tests for hypothyroidism?
- Free T4 by equilibrium dialysis
- Thyroglobulin antibodies TgAA
How might you treat hypothyroidism?
- Sodium levothyroxine
- Starting dose- 0.02mg/ kg
What monitoring might you do for hypothyroidism?
- Monitor 6-8 weeks after starting therapy
- Look for improvements in clinical signs
- Once stable -> recheck every 6 months
What is the clinical presentation for hyperthyroidism?
- Mass in neck
- > 60% metastasis
What causes 98% of hyperthyroid cases?
Adenoma/ Benign adenomatous hyperplasia
3% due to malignant thyroid carcinoma
What are the clinical signs of hyperthyroidism?
- Weight loss and increased appetite
- Behavioural changes
- Polyuria/ Polydipsia
- GI signs
- Heat and Stress Intolerance
What is palpable thyroid goitre?
Identifiable in 90% of cats with hyper T4- but not pathognomic
What cardiac disturbances does hyperthyroidism cause?
- Tachycardia is the most common
- Tachyarrhythmia, Gallop Rhythm
- heart murmurs
What does hyperthyroidism haematology look like?
- Erythrocytosis
- Heinz bodies on blood smear
What does hyperthyroidism biochemistry look like?
- Increased liver enzymes
- Azotaemia
What does hyperthyroidism urinalysis look like?
- Decreased USG
- glycosuria
How might you diagnose Hyperthyroidism?
Elevated TT4
What kind of imaging may help diagnose hyperthyroidism?
- Thyroid imaging/ Scintigraphy
- Echocardiography/ Cardiac assessment
What happens to the kidneys in an untreated hyperthyroidism state?
- Increased renal blood flow +GFR
- Protein catabolism
- Loss of muscle mass -> decreased creatinine
What is the MOA for anti-thyroid drugs?
Inhibit thyroid peroxidase enxymes
What are the indications for using anti-thyroid drugs?
Can either be short or long term treatment
What are the side effects for anti-thyroid drug usage?
- Anorexia, wasting, Vomiting
Head + Neck Pruritis and excoriations
What is the pre-surgical management for a thyroidectomy?
- Anti-Thyroid drugs- recommended for pre-surgical stabilisation of clinical signs
- anaesthetic safety
What are the potential risks/ complications of a thyroidectomy?
- Hypothyroidism
- Hypoparathyroidism
- Disease recurrence
What is the MOA for radioactive iodine?
thyroid cells concentrate RAI in the same way as regular iodine. When administered
(injectable or oral) → transported to thyroid follicular cells → incorporated into thyroglobulin →
beta ionising radiation → follicular cell death
