Case 9- Thyroid disorders Flashcards
What can synthetic thyroid hormones treat
Hypothyroidism (myxoedema), diffuse non-toxic goitre, Hashimoto’s thyroiditis (lymphadenoid goitre) and thyroid carcinoma
Aim of treatment for thyroid disorders
Replacing hormones not augmentation of thyroxine synthesis
Levothyroxine sodium (T4, thyroxine sodium)
First line treatment for hypothyroidism, maintenance therapy. The dose is adjusted according to response in the patient and is taken orally 30 min before meals/caffeine.
Liothyronine sodium (synthetic T3)
Used in severe hypothyroid states such as myxoedema coma, where a rapid response is needed. Patients may also need IV fluid and steroids as additional therapy in severe hypothyroidism conditions
What can thyroid disorders be mistaken for
An overdose may mimic hyperthyroidism and thyrotoxicosis and may cause cardiac arrhythmias, angina pectoris or cardiac failure. Hypothyroidism can be confused with ischaemia.
Causes of Hyperthyroidism
1) Thyrotoxicosis
2) Diffuse toxic goitre (Grave’s disease)
3) Toxic nodular goitre
Thyrotoxicosis
Overproduction of thyroid hormones. Presents with high metabolic rate, increase in skin temperature and sweating (heat tolerance), nervousness, tremor, increased appetite, weight loss and tachycardia. This can be caused by diffuse toxic goitre (Grave’s Disease) or due to toxic nodular goitre.
Diffuse toxic goitre (Grave’s disease)
An autoimmune disease targeting and activating TSH receptors leading to an increase in thyroxine secretion
Toxic nodular goitre
Caused by a benign tumour or adenoma which secretes thyroxine
Radioactive sodium iodide (131I)
Administered orally and is used for treatment of thyrotoxicosis at all ages. It is useful if drugs are not tolerated by the patient or when there are problems with compliance. Can be used when there is evidence of cardiac disease or following a relapse after thyroidectomy.
Mechanism of action of radioactive sodium iodide
It works by emitting beta and gamma radiation causing destruction of thyroid tissue. Loss of tissue makes it likely that the patient will require subsequent T4 replacement therapy.
Contradiction of radioactive sodium iodide
Children and during pregnancy
Diagnostic role of radioactive sodium iodide
It can be given at a tracer dose to assess thyroid function
Thioureylenes
Antithyroid dugs that are used to prepare patients for thyroidectomy or for long term management. Used to treat Hyperthyroidism
Carbimazole
Most commonly used antithyroid drug, decreases output of thyroid hormones. Used to treat Hyperthyroidism. Gradual reduction in signs and symptoms, after 4 weeks metabolic and pulse rate are back to normal. It inhibits the iodination of thyroglobulin
Carbimazole contraindications
Avoid during pregnancy
How long does carbimazole take to have its full effect
A long time as T4 has a long half life and may be stored
What other drugs can Carbimazole be combined with
Can be combined with levothyroxine sodium daily to form a blocking-replacement regimen which is given for an 18 month duration. You stop thyroid hormone production and then replace it with a more suitable amount.
Side effects of Carbimazole
Neutropenia (low white blood cells) and agranulocytes (lack of granulocytes). If evidence of bone marrow suppression or neutropenia then stop treatment. Avoid using in sever hepatic impairment. Over treatment can cause hypothyroidism, may cause foetal goitre.
Propylthiouracil
Used to treat hyperthyroidism. It is similar to carbiamazole but blocks T4 to T3 conversion in peripheral tissues. Its use is reserved for patients not responding to carbiamazole
Iodine/Iodide
Treatment for hyperthyroidism. Iodine is converted in-vivo to iodide. High doses of iodine inhibit secretion of thyroid hormones over 10-14 days. The underpinning mechanism is uncertain but may be due to reduced blood supply to the thyroid. High dose Iodine/Iodide may be used in preparation of patients for surgical resection.
Propanolol hydrochloride
Used in treating symptoms of hyperthyroidism such as tachycardia, arrhythmias and tremores. It is used alongside radioactive iodine treatment. Does’nt treat underlying cause.
Treatment for thyrotoxic crisis (thyroid storm)
IV fluid, propranolol hydrochloride, Hydrocortisone, oral iodine solution and Carbimazole or propylthiouracil.
Non-toxic goitre
Swelling of the neck, no change in thyroid hormone levels but a decrease in Iodide levels, can be treated with radioactive iodine. Causes hyperthyroidism
Hyperthyroidism
Excessive production and secretion of thyroid hormones leading to thyrotoxicosis (an excess of circulating thyroid hormone)
Signs and symptoms of hyperthyroidism
Goitre, hyperactivity, disturbed sleep, fatigue, palpitations, anxiety, heat intolerance, increased appetite with unintentional weight loss, and diarrhoea.
Overt hyperthyroidism
When TSH levels are below the reference range and T3 or T4 levels are above the reference range
Signs of Thyrotoxicosis
An acute presentation with pyrexia, tachycardia and delirium. You will admit the patient for monitoring, give them fluid resuscitation and anti-arrhythmic drugs
Exophthalmos
Bulging of the eyeball due to Grave’s disease, as a result of inflammation and swelling.
How to treat severe cases of hyperthyroidism
You can have surgery to remove the whole gland or just nodules. This stops production of the thyroid hormone. They will require Levothyroxine for life to replace TSH
Hypothyroidism
The underproduction and secretion of thyroid hormones
Signs and symptoms of hypothyroidism
Fatigue, weight gain, constipation, menstrual irregularities, depression, dry skin and thinning hair.
Complications of hypothyroidism
Coronary heart disease, impaired fertility, impaired concentration and pregnancy complications
Primary hypothyroidism
When the condition arises from the thyroid gland and may be caused by iodine deficiency, autoimmune disease (such as Hashimoto’s thyroiditis), radiotherapy, surgery or drugs, rather than due to a pituitary or hypothalamic disorder (secondary hypothyroidism).
Overt hypothyroidism
Decreased TSH and an increased T4 level
Thyroid function test
Identifies levels of TSH, T3 and T4
TPO antibodies
Raised in Grave’s
Thyroid disease- X-ray/ ultrasound/ biopsy
To assess the thyroid for cancer
How to manage overt hyperthyroidism
Overt hyperthyroidism is managed with beta blockers and carbimazole. Carbimazole may cause development of a rash but this can be treated with antihistamines.
