Thyroid Gland Flashcards
What level of TSH will you find in a patient with primary hypothyroidism, where the thyroid gland has been destroyed by the immune system?
a High TSH
b Low TSH
c Normal TSH
a
Describe the control of thyroid activity.
What medication do we use to treat primary hypothyroidism? How do we know when the dose is enough?
levothyroxine
increase dose until TSH falls to normal
Name an autoimmune disease that results in hypothyroidism.
Hashimotos
Describe Graves’ Disease
Describe the presentation of Grave’s Disease.
What causes exophthalmus in Graves’ disease?
Other antibodies bind to muscles
behind the eye and cause exophthalmos
can cause blindness
What is this?
Exophthalmos
What causes pretibial myxoedema in Graves’ disease?
Other antibodies cause pretibial myxoedema (hypertrophy)
What do we call the swelling (non-pitting) that
occurs on the shins of patients with Graves’ disease: growth of soft tissue?
Pretibial myxoedema
What is this?
Pretibial myxoedema
How would a radioactive iodine-reuptake scan of a Graves’ thyroid gland appear?
Diffuse goitre of moderate size and uniform radioiodine uptake
What is Plummer’s disease?
How does a pt with plummer’s disease present differently to a pt with Graves’
*NO pretibial myxoedema
*NO exophthalmos
How would a radioactive iodine-reuptake scan of a toxic nodular thyroid gland appear?
not smooth uptake
What effects does thyroxine have on the sympathetic nervous system?
Describe the presentation of a pt with hyperthyroidism?
*Weight loss despite increased appetite
*Breathlessness
*palpitations, tachycardia
*Sweating
*Heat intolerance
*Diarrhoea
*Lid lag and other sympathetic features
How do we diagnose and treat a thyroid storm?
- Medical emergency : 50% mortality untreated
- Blood results confirm hyperthyroidism
What is a thyroid storm characterised by?
What are the 3 treatment options for hyperthyroidism?
- surgery
- radioiodine
- drugs
What are the 4 classes of drugs used to treat hyperthyroidism?
- The thionamides (thiourylenes; anti-thyroid drugs)
- propylthiouracil (PTU)
- carbimazole (CBZ) - Potassium Iodide
- Radioiodine
- β-blockers
What effect does Potassium iodide bring about in regards to hyperthyroidism?
Wolff-Chakoff effect
Name 2 thionamides and what conditions we can use this drug to treat.
propylthiouracil
carbimazole
Graves’
Toxic thyroid nodule/toxic multinodular goitre
Describe the synthesis of thyroid hormone.
- Iodine is transported into the follicular cell via NaI co-transporter (I, 2Na)
- Na transported back out via NaKATPase
- I- transported across apical membrane into colloid
- Thyroperoxidase iodises tyrosine residues of thyroglobulin, making MIT and DIT.
- coupling reaction maing T3, rT3, T4
- Iodinated thyroperoxidase endocytoses back into follicular cell
- peroxidases cleave the T3 and T4
- exocytoses back into circulation
How do thionamides work?
inhibition of thyroid peroxidase and hence T3/4 synthesis and secretion
Why may clinicians prescribe propranolol to pt with hyperthyroidism?
rapidly reduces tremor, tachycardia
Name some unwanted actions of thionamides.
- Agranulocytosis (usually reduction in neutrophils) - rare and reversible on withdrawal of drug.
- rashes (relatively common)
What is the follow up treatment plan after starting antiithyroid drug?
What is the follow up treatment plan after starting
What is the role of b blockers in thyrotoxicosis?
When do we use KI to treat hyperthyroidism? What dose do we use?
- preparation of hyperthyroid patients for surgery
- severe thyrotoxic crisis (thyroid storm)
30x times the av daily requirement
What is the mechanism of KI in hyperthyroidism?
- inhibits H2O2 generation + thyroperoxidase
- inhibits iodination of thyroglobulin
Name some problem with thyroid surgery.
- Risk of voice change
- Risk of also losing parathyroid glands (hypocalcaemia)
- Scar
- Anaesthetic
How does radioiodine treatment work? What are some contraindications and precautions to do with this treatment?
*Swallow a capsule containing about 370 MBq (10 mCi) of the isotope I (131)
*Contraindicated in pregnancy
*Need to avoid children and pregnant mums for a few days
What do we use to image the thyroid gland that is not iodine?
99-Tc pertechnetate
(only for scans, not radioiodine treatment)
Describe the presentation / symptoms of Viral (de Quervain’s) thyroiditis?
Describe the natural history of viral thyroiditis.
Describe how the scan of someone with viral thyroditis may appear.
blank
What happens to the thyroxine in the thyroid gland in viral thyroiditis?
1 month hyper
1 month hypo
then euthyroid again
How does viral thyroditis differ from post -partum thyroiditis?
postpartum no pain, only occurs after pregnancy and most dont recover as immune system modulated during pregnancy
