Case 9- Thyroid disorders

Question 1

What can synthetic thyroid hormones treat

Answer 1

Hypothyroidism (myxoedema), diffuse non-toxic goitre, Hashimoto’s thyroiditis (lymphadenoid goitre) and thyroid carcinoma

Question 2

Aim of treatment for thyroid disorders

Answer 2

Replacing hormones not augmentation of thyroxine synthesis

Question 3

Levothyroxine sodium (T4, thyroxine sodium)

Answer 3

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.

Question 4

Liothyronine sodium (synthetic T3)

Answer 4

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

Question 5

What can thyroid disorders be mistaken for

Answer 5

An overdose may mimic hyperthyroidism and thyrotoxicosis and may cause cardiac arrhythmias, angina pectoris or cardiac failure. Hypothyroidism can be confused with ischaemia.

Question 6

Causes of Hyperthyroidism

Answer 6

1) Thyrotoxicosis
2) Diffuse toxic goitre (Grave’s disease)
3) Toxic nodular goitre

Question 7

Thyrotoxicosis

Answer 7

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.

Question 8

Diffuse toxic goitre (Grave’s disease)

Answer 8

An autoimmune disease targeting and activating TSH receptors leading to an increase in thyroxine secretion

Question 9

Toxic nodular goitre

Answer 9

Caused by a benign tumour or adenoma which secretes thyroxine

Question 10

Radioactive sodium iodide (131I)

Answer 10

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.

Question 11

Mechanism of action of radioactive sodium iodide

Answer 11

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.

Question 12

Contradiction of radioactive sodium iodide

Answer 12

Children and during pregnancy

Question 13

Diagnostic role of radioactive sodium iodide

Answer 13

It can be given at a tracer dose to assess thyroid function

Question 14

Thioureylenes

Answer 14

Antithyroid dugs that are used to prepare patients for thyroidectomy or for long term management. Used to treat Hyperthyroidism

Question 15

Carbimazole

Answer 15

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

Question 16

Carbimazole contraindications

Answer 16

Avoid during pregnancy

Question 17

How long does carbimazole take to have its full effect

Answer 17

A long time as T4 has a long half life and may be stored

Question 18

What other drugs can Carbimazole be combined with

Answer 18

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.

Question 19

Side effects of Carbimazole

Answer 19

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.

Question 20

Propylthiouracil

Answer 20

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

Question 21

Iodine/Iodide

Answer 21

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.

Question 22

Propanolol hydrochloride

Answer 22

Used in treating symptoms of hyperthyroidism such as tachycardia, arrhythmias and tremores. It is used alongside radioactive iodine treatment. Does’nt treat underlying cause.

Question 23

Treatment for thyrotoxic crisis (thyroid storm)

Answer 23

IV fluid, propranolol hydrochloride, Hydrocortisone, oral iodine solution and Carbimazole or propylthiouracil.

Question 24

Non-toxic goitre

Answer 24

Swelling of the neck, no change in thyroid hormone levels but a decrease in Iodide levels, can be treated with radioactive iodine. Causes hyperthyroidism

Question 25

Hyperthyroidism

Answer 25

Excessive production and secretion of thyroid hormones leading to thyrotoxicosis (an excess of circulating thyroid hormone)

Question 26

Signs and symptoms of hyperthyroidism

Answer 26

Goitre, hyperactivity, disturbed sleep, fatigue, palpitations, anxiety, heat intolerance, increased appetite with unintentional weight loss, and diarrhoea.

Question 27

Overt hyperthyroidism

Answer 27

When TSH levels are below the reference range and T3 or T4 levels are above the reference range

Question 28

Signs of Thyrotoxicosis

Answer 28

An acute presentation with pyrexia, tachycardia and delirium. You will admit the patient for monitoring, give them fluid resuscitation and anti-arrhythmic drugs

Question 29

Exophthalmos

Answer 29

Bulging of the eyeball due to Grave’s disease, as a result of inflammation and swelling.

Question 30

How to treat severe cases of hyperthyroidism

Answer 30

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

Question 31

Hypothyroidism

Answer 31

The underproduction and secretion of thyroid hormones

Question 32

Signs and symptoms of hypothyroidism

Answer 32

Fatigue, weight gain, constipation, menstrual irregularities, depression, dry skin and thinning hair.

Question 33

Complications of hypothyroidism

Answer 33

Coronary heart disease, impaired fertility, impaired concentration and pregnancy complications

Question 34

Primary hypothyroidism

Answer 34

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).

Question 35

Overt hypothyroidism

Answer 35

Decreased TSH and an increased T4 level

Question 36

Thyroid function test

Answer 36

Identifies levels of TSH, T3 and T4

Question 37

TPO antibodies

Answer 37

Raised in Grave’s

Question 38

Thyroid disease- X-ray/ ultrasound/ biopsy

Answer 38

To assess the thyroid for cancer

Question 39

How to manage overt hyperthyroidism

Answer 39

Overt hyperthyroidism is managed with beta blockers and carbimazole. Carbimazole may cause development of a rash but this can be treated with antihistamines.