REduction of LEvothyroxine in Adults; a SElf controlled study

Many older persons in the Netherlands use levothyroxine (2015: >215.000 aged 65+), and often have been using levothyroxine for a very long time. Initial indications for treatment are often not well registered, inaccurate or even inappropriate due to changing guidelines. Currently, levothyroxine treatment is indicated for patients with overt hypothyroidism (high Thyroid Stimulating Hormone [TSH], low free Thyroxin [fT4]). For subclinical hypothyroidism (high TSH, normal fT4), the most common thyroid disorder in older people (3-18% aged 65+), guidelines vary. Recently, in the TRUST trial, it was shown that levothyroxine treatment was not clinically beneficial in people aged 65 years and older with subclinical hypothyroidism. Given the high prevalence of levothyroxine use, the ambiguous treatment indications, the lack of evidence for beneficial effects of treatment and the health risks associated with (over)treatment, we hypothesize that discontinuation of levothyroxine is feasible in many older persons without negative consequences.
An self-controlled observational study will be performed investigating the stepwise reduction of levothyroxine treatment in persons aged 60 years and older. The primary aim is to study what proportion of participants that withdraw their levothyroxine successfully, defined as having normal fT4 levels and TSH levels <10 mU/L at 52 weeks after start of the discontinuation.

At least 50% of older patients using levothyroxine treatment can be withdrawn successfully and safely.

Run-in period (from t = -12 weeks): baseline measurement of thyroid function (TSH and fT4), questionnaires, continuation of levothyroxine treatment.
Discontinuation phase (from t = 0 weeks): stepwise reduction of levothyroxine based on measurements of TSH and fT4; questionnaires.
Follow-up phase: measurement of thyroid function and questionnaires.

Stepwise reduction of levothyroxine treatment.