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Q If TSH is rising but thyroxine is normal, what should I do?
A The persistently abnormal results exclude transient thyroid dysfunction. The hypothyroid phase of a thyroiditis should not last longer than a few weeks. An elevated TSH with normal thyroid hormone levels is sub-clinical hypothyroidism.
The decision to treat is based on the likelihood of conversion to frank hypothyroidism (more likely if the patient has a family history, a goitre or has detectable thyroid antibodies) and the probability that the patient will benefit from thyroxine replacement.
A trial of thyroxine would be reasonable for convincing hypothyroid symptoms, especially in the presence of the above associated factors.
But if the TSH is greater than 10miu/l then current consensus would be to start treatment, although evidence that symptoms improve is inconclusive.
There is no definitive data to suggest those with subclinical hypothyroidism (TSH<10miu )="" have="" any="" clear-cut="" benefit="" from="" thyroxine="" therapy,="" although="" some="" studies="" do="" show="" benefits="" on="" lipid="" profiles="" and="" psychometric="" function="" with="" a="" much="" lower="">10miu>
A progressive rise in TSH suggests they may develop frank hypothyroidism and treatment with thyroxine would be reasonable. Treatment goals are the same as frank hypothyroidism, ie, a TSH within the normal range, ideally close to 1miu/l.
Therapy should be reviewed and continued only in the presence of benefit. If thyroxine is not initiated then the thyroid function should be checked every three-six months.
Dr David Gable, specialist registrar, and Dr Steven Hurel, Consultant Endocrinologist, Department of Diabetes and Endocrinology,
University College Hospitals, London