Treatment of Thyroid Disorders Flashcards
Name the three hormones secreted by the thyroid gland
Thyroxine
Triiodothyronine
Calcitonin
What are the main steps involved in the synthesis of thyroid hormones?
- Uptake of plasma iodide by the follicle cells.
- Oxidation of iodide and iodination of tyrosine residues in thyroglobulin of the colloid.
- Secretion of the thyroid hormone
Describe some features of hypothyroidism
- Low free T4, possibly low T3 and raised TSH.
- Long term complications include cardiovascular disease
What are some of the causes of hypothyroidism?
Congenital, Autoimmune thyroiditis, Iatrogenic (post thyroidectomy or radio-iodine treatment), Drug induced (lithium, amiodarone), Pituitary disease
What are the causes of congenital hypothyroidism
- Absent thyroid (agenesis),
- Under developed (dysgenesis),
- Familial enzyme defects,
- Iodine deficiency,
- Intake of goitrogens during pregnancy,
- Idiopathic.
All babies are screened for hypothyroidism at birth
Describe features of Hashimoto’s?
- Most common cause of hypothyroidism,
- Autoimmune lymphocytic thyroiditis
Describe the relationship between amiodarone and the thyroid
Amiodarone has very close structural resemblance to thyroid hormones
What are the symptoms of hypothyroidism
- Tiredness,
- Weight gain,
- Feeling cold,
- Constipation,
- Dry or thinning hair,
- Hoarse voice,
- Pins and needles,
- Low mood,
- Memory problems
Explain the management of primary hypothyroidism
- Levothyroxine (synthetic analogue of thyroxine.
- Aim to maintain TSH within reference range.
What are the causes of hyperthyroidism
- Autoimmune (Graves),
- Toxic multinodular goiter,
- de Quervain’s thyroiditis,
- Medication (overtreatment with levothyroxine),
- Pituitary adenoma (tumour producing excess TSH),
- Transient neonatal thyrotoxicosis (mother with graves).
- Thyroid adenoma (rare)
Describe features of graves disease
- Autoimmune disorder mediated by antibodies that stimulate TSH.
- Clinical features are diffuse goitre, pretibial myxoedema, thyroid eye disease and acropathy.
Describe features of toxic multinodular goitre
- Small benign nodules within the thyroid gland. They are unresponsive to secretory control mechanisms and therefore secrete excess T3 and T4.
- Iodine deficiency is the most common cause
Describe features of de Quervain’s (subacute thyroiditis)
Painful swelling of thyroid gland triggered by a viral infection.
What are the symptoms of hyperthyroidism
- Anxiety,
- Palpitations,
- Weight loss,
- Goitre,
- Hair loss,
- Fatigue,
- Diarrhoea,
- Sweating,
- Muscle weakness,
- Insomnia,
- Periods are lighter/infrequent
What are the treatments for hyperthyroidism?
- Radioactive iodine,
- Anti thyroid medications,
- Symptomatic treatment,
- Surgery
What is the first line anti-thyroid drug and its features?
Carbimazole which gets metabolised to methimazole which directly inhibits thyroid hormone synthesis. Does this by inhibition of thyroperoxidase which reduces iodination of thyroglobulin.
May take several weeks to work
What are the main side effects of carbimazole
- Neutropenia and agranulocytosis,
- Skin rashes,
- Pancreatitis
- Increased risk of congenital malformations
What is the 2nd line treatment and its features
Propylthiouracil. Given to patients who experience side effects with carbimazole or pregnant/trying to conceive.
Side effects - agranulocytosis, bone marrow disorders, hepatic impairment.
What are other medications used in hyperthyroidism?
Thyroid hormones increase number of receptors, particular beta adrenoceptors which causes tachycardia, hypertension and increased risk of dysrhythmias, tremors, and agitation. So beta blockers such as propranolol is often used adjunct to anti-thyroid therapy
When is surgery appropriate for hyperthyroidism?
- Total thyroidectomy for adults with grave’s disease
What are potential complications of thyroid surgery?
- Haemorrhage, infection, damage to laryngeal nerve, hypothyroidism, hypocalcaemia, hypoparathyroidism
Describe features of radioactive iodine?
It is given orally and is selectively taken up by thyroid.
- Given as single dose which lasts 2 months.
- Not suitable before puberty.
- Avoid contact with pregnant women and small children.
What is the block and replace regimen?
High dose carbimazole with levothyroxine.
