Thyroid Flashcards
What does the thyroid secrete?
thyroxine - T4
triiodothyronine - T3
calcitonin
- regulates calcium levels = causes reduction
unbound hormone is active
- can be bound to thyroxin binding globulin
What are thyroid function tests?
are used for
- diagnostic testing to identify and classify any disorders of thyroid functioning
- monitoring the effects of a known thyroid disease
tests for
- thyroid stimulating hormone (TSH)
- total or free T4
- total or free T3
How do T4, T3 and TSH levels correlate?
negative feedback cycle
high T4 and T3 = low TSH
low T4 and T3 = high TSH
TSH takes time to adjust
- must wait weeks to monitor
What is thyrotoxicosis? What are the symptoms?
What are the symptoms of hypothyroidism?
hyperthyroidism = excessive thyroid hormones
- weight loss, palpitations, tremor, sweating , increased appetite, goitre, heat intolerance, fatigue, diarrhoea, irritability, lid lad
hypothyroidism
- weight gain, bradycardia, lethargy, dryness and coarsening of skin and hair, constipation, goitre, hoarseness, cold intolerance
What is thyroiditis? How can be it be treated?
inflammation of the thyroid gland
caused by
- viral or sub-acute thyroiditis = has flu-like symptomology
- post partum thyroiditis
- drug induced thyroiditis
- autoimmune thyroiditis
need steroids or NSAIDs
What drugs affect thyroid functioning?
amiodarone - can cause hypo or hyperthyroidism
lithium - causes hypothyroidism
GLP-1 agonist can cause thyroid cancer
glucocorticoids and dopamine can lower the serum TSH level
How is hypothyroidism treated?
levothyroxine
- 100-200mcg per day
= is given orally
liothyronine sodium
- 10-20mcg per day
= is more potent than levothyroxine and is used in severe hypothyroid state/coma
= can be given orally or via slow i.v injection
What are the causes of hypo and hyperthyroidism?
hypothyroidism
- autoimmune destruction of thyroid gland = Hashimoto’s disease
- radioiodine or surgical treatment of hyperthyroidism
- drug induced = lithium carbonate
- hypopituitarism
hyperthyroidism
- Grave’s disease
- tumours
- toxic multi nodular goitre
- drug induced
How is hyperthyroidism treated?
carbimazole
- inhibits thyroxine peroxidase
= 15-40mg daily then titrated down after becoming euthyroid
- can cause agranulocytosis = mouth ulcers, sore throat
propylthiouracil
= 200-400mg daily then titrated down after becoming euthyroid
blocking replacement regimen
- carbimazole and thyroxine = to block and replace thyroid function
radioiodine
- destroys part of the thyroid gland to render them euthyroid
- CI in pregnancy and breastfeeding
Why are beta blockers used in hyperthyroidism?
are used for rapid symptomatic release while antithyroid drugs kick in
- can take 10-12 days for carbimazole, months for radioiodine
propranolol, nadolol
How are patients prepared for surgery to treat hyperthyroidism? What are complications associated? What treatment are they given after?
must be rendered euthyroid using carbimazole
antithyroid drugs must be stopped 10-14 days prior to surgery and replaced with oral potassium iodine
hypocalcaemia - need calcium
hypothyroidism - need levothyroxine for life
hypoparathyroidism - need calcium and vitamin D
What monitoring is required after using antithyroid drugs or having surgery?
ATD
- TSH, T4 and T3 every 6 weeks until TSH is normal then TSH every 3 months after
Surgery
- TFTs at 2 months and 6 months then annually
What is a thyroid crisis? How is it treated?
rapid thyrotoxicosis with hyperpyrexia, tachycardia, extreme restlessness and eventual delirium, coma then death
- caused by infection, trauma/stress, surgery or radioiodine
management
- large doses of carbimazole, propranolol and iodine to block thyroid hormone release
- dexamethasone or hydrocortisone to inhibit peripheral conversion of T4 to T3 (more potent form)
What test should be carried out if a patient taking carbiamazole complains of a sore throat? Why?
neutrophil count
- due to risk of agranulocytosis
