The diagnosis of an underactive thyroid gland is confirmed with below normal serum thyroxine levels. Also known as myxoedema.

Suspicious nodules

Any patient in whom a solitary nodule, a suspicious or dominant nodule within a multinodular goitre, or lymph nodes are palpated requires urgent ultrasound guided aspiration.

Suspected eye disease

Patients with suspected eye disease require evaluation by an endocrinologist or ophthalmologist experienced in Graves' ophthalmopathy. Simple lubricants, avoidance of smoky environments and avoidance of bright sunlight and strong winds by wearing sunglasses should be advised in all patients with Graves’ ophthalmopathy.

Detailed guidance on assessment, referral criteria and treatments are given in the section on Graves' ophthalmopathy. An explanatory leaflet is also available from the British Thyroid Association.

All patients with auto-immune thyroid disease should be advised to stop smoking

Smoking increases the risk of developing new ophthalmopathy, increases the severity of existing ophthalmopathy, reduces the efficacy of treatment for ophthalmopathy, and increases the risk of ophthalmopathy deteriorating or developing de novo following radioactive iodine treatment.

General advice must be given and referral to a formal smoking cessation clinic discussed.

Assess cardiac status and risk factors

Any patient with severe clinical or biochemical hypothyroidism should be assessed for cardiac disesase and risk factors before starting replacement therapy. 

Standard replacement therapy

Usual starting dose is 50mcg thyroxine. The dose can then be increased after two weeks if tolerated to 100mcg. Thyroid stimulating hormone (TSH) should then be reassessed at around six weeks and 12 weeks and dose titrated accordingly, aiming for good improvement in symptoms and a normal TSH.

In patients with mild biochemical hypothyroidism, it may be appropriate to remain on 50mcg and reassess at approximately six weeks, though 100-150mcg are typical adult doses.

Subsequent monitoring of TSH should be at three months and six months, then annually is sufficient. Symptoms do not always completely resolve, leading some patients to consider alternative treatments including combined liothryonine and thyroxine, and natural thyroid extracts. This is not standard practise in the UK.

Patient information sheets on this subject are available from the British Thyroid Association.

Low dose treatment initiation

25mcg thyroxine is suitable for most patients with severe biochemical disease. However, patients with severe hypothyroidism and unstable cardiac disease, will require very gentle initiation of therapy. Liothyronine is short acting and may be started in extremely low doses in such cases. Tiny doses as low as 1.25mcg may be used in very severe cases, and titrated over a two week period up to 30mcg daily in divided doses. Patients tolerating this with no adverse effects, can be switched to thyroxine 25mcg, which is then uptitrated every six weeks according to symptoms and aiming for a normal serum TSH.

Pregnancy and fertility plans should be discussed with all patients

Patients who are planning or are currently pregnant should be treated with the aim of achieving a TSH of <2.5mU/L according to latest guidance.

Patients should be advised that thyroxine requirements invariably increase with pregnancy and many services suggest a dose increase of 25mcg as soon as pregnancy is confirmed.

It is appropriate to monitor TSH every three months during pregnancy and breast feeding, and six weeks after any dose adjustment to ensure that the dose is appropriate. Most patients revert to their prepregnancy dose post partum.

Long term monitoring

Long term monitoring should be performed by the general physician and may take the form of an annual TSH only.