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Sub Clinical hypothyroidism

Checked: 23-08-2021 by Vicky Ryan Next Review: 23-08-2022

Overview

These guidelines have been provided by the Endocrinology Team at NBT so pathways might be slightly different at UHBW

Important points

Affects 4-20% of the adult population but approximately one third experience no symptoms. Others report symptoms that are characteristic of overt hypothyroidism.

Further investigation

If the TSH is above the upper limit of the reference range, repeat 3 months later with TPO antibody assessment
When considering whether to commence treatment, always take a history regarding symptoms of hypothyroidism in addition to risk factors predicting progression to overt hypothyroidism e.g. family history of thyroid disease, previous thyroid surgery/radioiodine treatment
Consider treatment with Levothyroxine for sub clinical hypothyroidism in the following case:
- If the thyroid-stimulating hormone (TSH) level is ≥10mU/L and the fT4 level is within the reference range on 2 separate occasions 3 months apart
Consider offering a 6-month trial of LT4 monotherapy in adults less than 65 years of age if:

The TSH level is above the reference range but ≤10 mU/L and fT4 is within the reference range on 2 separate occasions 3 months apart and
There are symptoms of hypothyroidism
If symptoms do not improve after starting LT4 therapy measure the TSH level and if it remains raised, adjust the dose of LT4. Once the TSH level is stable (2 similar measurements within the reference range 3 months apart), check TSH annually
If symptoms persist when the TSH is within the reference range, consider stopping LT4 therapy, and assess for alternative causes of symptoms

If asymptomatic with a TSH between 5mU/l and 10mU/l, measure TPO antibodies (predicts likelihood of progression to overt hypothyroidism)

If antibody negative, measure TSH 3 yearly
If antibody positive, measure TSH annually

Resources

References:

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