The treatment of hypothyroidism is thyroid replacement for life. The decision whether to treat hypothyroidism depends on the clinical situation. If there is overt clinical hypothyroidism and the TSH is above the reference range then the patient should be treated.
If there is subclinical hypothyroidism and the TSH ranges from 6 to 10 mU/l and thyroxine levels are within the reference range the management is controversial. It is known that such patients with positive antibodies have a conversion rate to overt hypothyroidism of around 5% per year. Those patients with little or no symptoms can be safely watched with a yearly clinical review. If the antibodies are negative the review can be safely done every three years. When patients have symptoms consistent with hypothyroidism a therapeutic trial of thyroxine for up to 6 months is justified. If the symptoms vanish then thyroxine for life is justified if not it should be stopped.
If there is controversy about the treatment of subclinical hypothyroidism there is uproar about the treatment of the alleged hypothyroid patient with TSH levels well within the reference range. The general view in the UK is that such patients are not hypothyroid and do not need treatment with thyroxine. Thyroxine therapy when clinically indicated is not without its dangers. Studies in the USA and the UK have shown that a high percentage of patients on thyroxine take the wrong dose risking the development of heart and bone disease. There is a view among some doctors and some members of the lay public that thyroxine is indicated for patients with a TSH within the reference range who have symptoms suggestive if hypothyroidism. The argument is that most doctors are treating the biochemistry and not the patient and that the upper limit of the TSH reference range should be lowered to 2.5mU/l. Mr Lynn does not support this view. The argument has been heated and has been presented to members of the UK Parliament and to the General Medical Council. Despite most endocrinologists objections to the unnecessary use of thyroxine it is only fair that patients are aware of the discussion which can be found on www.thyroidtears.co.uk.
The replacement drug of choice is levothyroxine (T4), which is converted in the body to the active hormone T3. A single T4 tablet has a long life in the body and its effect lasts for several weeks. This plus the fact that the conversion from T4 to T3 is constant and stable makes T4 an ideal drug in hypothyroidism. In the young the treatment is simple, starting with 1.6 micrograms per kilogram body weight, this is usually around 0.1mgs a day for women and 0.125mgs for men, increasing the dose until the TSH is about 2.0 mU/L. The tablets are best taken on an empty stomach before breakfast. In subclinical hypothyroidism it is best start with the calculated full replacement dose aiming at a TSH of 2.5 iU/l or lower. It must be remembered that that TSH may take 3 to 6 months to return to well within the reference range.Dose requirements will change with age, pregnancy, and gross weight change. Calcium salts, ferrous sulphate, aluminium hydroxide and cholestyramine all reduce the absorption of thyroxine. These medications should be taken at a different time in the day to thyroxine. Certain drugs increase the clearance from the body of thyroxine these include phenytoin, carbamazepine, phenobarbitone and rifampicin. Patients taking these drugs should have the TSH checked often as larger doses of thyroxine than usual may be necessary to obtain a satisfactory TSH.
The problem of a persistently raised TSH despite an adequate replacement dose of thyroxine is common and almost always due to haphazard taking of thyroxine. In non compliant patients the total weekly dose may be taken on a single day in the week. This regime is safe and usually effective. Rarely this not the case and a change of thyroid brand may be considered.
If on treatment the patient still does not feel well and the TSH is below 2.5mU/L then the diagnosis of hypothyroidism is almost certainly wrong and alternative diagnoses must be considered.
There has been considerable discussion about the use of a combination of T4 and T3 and desiccated pig thyroid extract (Armour Thyroid) in the management of hypothyroidism. This issue has been reviewed by the British Thyroid Association (BTA) Executive Committee in November 2007. I will quote extensively from their document which can be reviewed at www.british-thyroid-association.org
The BTA states:
#1. There is no evidence now that T4/T3 combination is better than T4 alone in controlling symptoms. Some studies have showed harmful effects of combination therapy.
#2. Despite the above some patients preferred combination T4/T3therapy - the reason for this is a mystery.
#3. There is no preparation that contains the same ratio of T4/T3 as secreted by the human thyroid.
#4. The BTA has an open mind as to whether in the future an appropriate formulation T4/T3 combination tablet will have a role to play in a subgroup of hypothyroid patients but do not feel they can recommend its use at the present time.
#5. Armour Thyroid is not recommended by the BTA. Its ratio of T4 to T3 not physiological and its stability is variable and resulted in a massive recall of tablets in the past.
#6. Armour Thyroid is not licensed in the UK but can be prescribed in the UK on a named patient basis.
Despite the concerns of the BTA it must be admitted that one sees patients who feel that changing to Armour Thyroxine has changed their lives. Mr Lynn will not initiate treatment with Armour Thyroxine but if the patient is already on Armour Thyroxine and are well he agrees to its use. Mr Lynn does however find the evaluation of the bichemistry very difficult in patients on Armour Thyroid. The Armour Thyroid website is www.armourthyroid.com
Despite the stance of the BTA it must be remembered that there has not been a single randomised blind trial comparing Armour Thyroid against thyroxine.
In the elderly or frail a cautious approach is used with careful monitoring of the heart and replacement starting with doses as low as 0.025 mgs of T4 per day, slowly increasing the dose until the TSH is normal. Improvement is slow and may take very many months.