Hypothyroidism

Causes

Autoimmune thyroiditis
Hashimoto's thyroiditis (autoimmune thyroiditis and goitre; a positive test resultfor the thyroid autoantibodies antithyroglobulin and antiperoxidasewill confirm the diagnosis)
Subacute thyroiditis (tender thyroid)
Amiodarone, lithium, interferonalfa, interleukin 2, macrophage colony stimulating factor, andoral and topical iodine are recognised causes of thyroid dysfunction.
Check for history of thyroid surgery or head and neck irradiationand radioactive iodine therapy for thyrotoxicosis.

Diagnosis

Clinical symptoms of hypothyroidism with a raised TSH +/- thyroid microsomal autoantibodies.
Subclinical hypothyroidism (elevated TSH without symptoms) should be managed according to the presence of thyroid microsomal antibodies:
- Autoantibodies present: commence thyroxine.
- Autoantibodies absent and TSH less than 10mU/l should be managed by watchful waiting.
Patients receiving long term lithium and amiodarone should also be monitored regularly.

First Visit

Check:

neck
eyes
weight
cardiac state
symptoms of IHD
FBC, lipids, glucose, autoantibodies, TFT
Discuss and agree a clear treatment and monitoring plan with patient. Explain that treatment is likely to be life long, that treatment at the correct dosage has no serious side effects, and that the prognosis is excellent. Tell patient that it may take a few weeks for thyroxine to begin working and that patient should not expect all symptoms to disappear within a few days of starting treatment.
Tell patient that she is entitled to free prescriptions and to fill in the prescription charge exemption certificate.

Indications for referral

Pregnant or post partum
Evidence of pituitary disease
Ischaemic heart disease
Treatment with amiodarone or lithium

Follow-up

Under 65

Thyroxine 50 micrograms daily
4 weekly check of

TSH
T4
Weight
Cardiac State

Increasing Thyroxine by 50 micrograms daily until TSH is within normal range. TSH levels below the normal range may increase risk of atrial fibrillation.

Over 65 and/or Ischaemic Heart Disease

Thyroxine 25 micrograms daily
4 weekly check of

TSH
T4
Weight
Cardiac State

Increasing Thyroxine by 25 micrograms daily until TSH is in the normal range. A suboptimal dose may be necessary with angina or cardiac failure. TSH elevated despite Thyroxine dose 150-200 micrograms daily is probably due to non-compliance. TSH levels below the normal range may increase risk of atrial fibrillation.

Subsequently check T4 and TSH every 12 months.

Websites with information on thyroid disorders

	Thyroid UK,a support group for patients (www.thyroiduk.org/)
	The US site About.com has excellent information (www.thyroid.about.com/)
	BritishThyroid Foundation (www.btf-thyroid.org/)
	The Royal National Institute for the Blind website's "Eye info" section has informationon thyroid eye disease (www.rnib.org.uk)

Audit standard

100% of patients on thyroxine should have a current problem Hypothyroidism .
100% of patients with hypothyroidism should have had their thyroid function checked within 15 months.
100% of patients taking amiodarone or lithium should have had their thyroid function checked within 15 months.

References:

Drug and Therapeutics Bulletin Jan 1998
10-minute consultation: Newly diagnosed hypothyroidism
H U Rehman and T A Bajwa
http://bmj.com/cgi/content/full/329/7477/1271?etoc