Management of Iatrogenic Hyperthyroidism and Pruritus

Evaluation and Adjustment of Thyroid Hormone Dose

The American College of Endocrinology recommends reducing the levothyroxine dose by 12.5-25 mcg immediately in patients with iatrogenic hyperthyroidism, as a TSH level of 0.21 mIU/L indicates thyroid suppression, increasing the risk of atrial fibrillation, bone loss, and cardiovascular complications 1
For patients with a TSH level between 0.1-0.45 mIU/L, a dose reduction of 12.5-25 mcg is recommended, particularly if the patient is symptomatic 1
Approximately 25% of patients on levothyroxine are inadvertently maintained on doses sufficient to completely suppress TSH, increasing the risk of severe complications 1

The British Journal of Dermatology guidelines suggest testing thyroid function only if the patient has additional clinical characteristics suggesting thyroid disease, as pruritus can be a manifestation of iatrogenic hyperthyroidism, although the association between thyroid disease and pruritus is rare (affecting approximately 27% of patients with thyroid disease) 2
Normalizing thyroid function should improve pruritus if it is truly causative 2
The British Journal of Dermatology recommends providing self-care advice (keeping nails short) and prescribing emollients as first-line treatment for pruritus, with antihistamines used for a short period if justified 3
Elderly patients may benefit from gabapentin for pruritus, but sedating antihistamines should be avoided 3, 4

After dose reduction, TSH and free T4 should be rechecked in 6-8 weeks 1
Once the appropriate dose is established, TSH should be monitored annually or sooner if symptoms change 1
Patients with generalized pruritus where the underlying systemic cause is not evident should be regularly followed up 3

Never ignore a suppressed TSH in symptomatic patients, as this perpetuates cardiovascular and bone risks 1
Do not attribute all symptoms to the thyroid, as pruritus can have multiple causes requiring appropriate investigation 3, 2
Avoid sedating antihistamines in elderly patients due to the increased risk of dementia 4
Do not adjust doses too frequently before reaching a steady state (wait 6-8 weeks between adjustments) 1