Thyroid conditions Flashcards
What are the two forms of the Thyroid hormone?
T3 and T4
What is T3?
Tri-iodothyronine
What is T4?
Thyroxine
What is TSH?
Thyroid Stimulating Hormone
Where is TSH released from?
The Anterior Pituitary gland
What is Hyperthyroidism characterised by?
LOW TSH levels and HIGH T3 and T4 levels
Why does Hyperthyroidism occur?
Too much T3 and T4 being produced by the thyroid gland and the negative feedback loop causes the Anterior Pituitary gland to stop production of TSH.
What is Hypothyroidism characterised by?
HIGH TSH levels and LOW T3 and T4 levels
Why does Hypothyroidism occur?
Insufficient T3 and T4 produced from Thyroid gland results in the negative feedback loop to produce more TSH from the Anterior Pituitary gland.
What are the common signs and symptoms of Hypothyroidism?
Slow speech, intolerance to cold, memory loss, depression, constipation, weight GAIN, dry skin, thin hair, BRADYcardia
What are the treatments for Hypothyroidism (under-active thyroid)?
Levothyroxine (artificial T4) or Liothyronine (artificial T3, if Hypothyroidism is severe)
What is the start dose for Levothyroxine?
50-100 mcg OM (25 mcg in patients 65+ yrs). Dose to be increased by 25-50mcg if TSH levels remain high. –> (1.6mcg/kg)
What are the common signs and symptoms of Hyperthyroidism?
Palpitations, TACHYcardia, sweating, tremor, anxiety, diarrhoea, intolerance to heat, weight LOSS, numerous eye problems (exophthalmos (bulging of the eyes), swelling of eyelids, lid retraction, ophthalmoplegia (weakening of eye muscles) and diplopia (double vision)
What are the symptomatic treatments for Hyperthyroidism (over-active thyroid)?
Propranolol for symptomatic treatment of tremor, palpitations and sweating
Why is Bisoprolol not appropriate for symptomatic treatment of Hyperthyroidism?
This is because Bisoprolol is beta-1 selective (cardio selective) and would only relieve the patient of the palpitations and not the sweating and tremor.
Why is Propranolol preferred over Bisoprolol for symptomatic treatment of Hyperthyroidism?
Because it is non-selective at beta receptors. It is more likely to control all of the symptoms. Bisoprolol is selective a beta-1 receptors in the heart.
What anti-thyroid drugs are available for treatment of Hyperthyroidism?
First line: Carbimazole
Second line: Propylthiouracil (when patient cannot tolerate Carbimazole)
What main counselling point is there for Carbimazole?
Be wary of any sore throats, easy bruising/bleeding. If you experience any of these, go to your GP immediately and stop taking Carbimazole.
What other treatments are available for Hyperthyroidism?
Radioactive Iodine treatment, or Surgery (Thyroidectomy). Patients will require Levothyroxine treatment after these.
What therapeutic monitoring parameters should be considered with Levothyroxine treatment?
Thyroid Function Tests and keeping an eye out for symptoms
What toxic monitoring parameters should be considered with Levothyroxine treatment?
Thyroid Function Tests (risk of HYPERthyroidism) and symptoms (goitre, bulging eyes, tachycardia).
What therapeutic monitoring parameters should be considered with Carbimazole treatment?
Thyroid Function Tests and symptoms
What toxic monitoring parameters should be considered with Carbimazole treatment?
Thyroid Function Tests, symptoms and any signs of bone marrow suppression (neutropenia/ anaemia and sore throat/coughing.
What is Primary Hypothyroidism?
Failure of the thyroid gland
What is secondary Hypothyroidism?
Anterior Pituitary dysfunction resulting in low TSH levels
What is tertiary Hypothyroidism?
Hypothalmic dysfunction resulting in low levels of TRH
What is Hashimoto’s thyroiditis?
An autoimmune condition where the body makes antibodies to thyroglobulin and causes hypothyroidism.
What is Grave’s disease?
Grave’s disease is an autoimmune condition with a genetic
predisposition, where the body makes thyroid-stimulating
antibodies that mimic TSH, stimulating the TSH receptor in the
thyroid gland.
What is the mechanism of action of thioureylenes (Carbimazole)?
They inhibit the synthesis of thyroid hormone (T4). Inhibition of thyroperoxidase means that tyrosine residues on thyroglobulin are not iodinated.
Why do people experience tremors and palpitations in Hyperthyroidism?
Because overstimulation of the thyroid gland (excess thyroid hormone) causes an up-regulation of beta-adrenergic receptors in heart and lungs.
How is the thyroid hormone synthesised?
TSH binds to GPCRs on epithelial cells in thyroid gland which cause an uptake of iodide ions. The iodide ions (I-) are actively transported into the follicle cells in the Thyroid gland via the Na+/I- co-transporter. Iodide ions are converted into Iodine by thyroid peroxidase. Thyroglobulin then binds its many tyrosine residues to Iodine. Monoiodotyrosine and Diiodotyrosine are used to create T3 and T4 respectively.
