5.2.7 Hypothyroidism

Treatment with TKI may cause hypothyroidism. The patient is usually asymptomatic and this is detected by measuring TSH and the peripheral hormones (T3/T4) in the blood. The cause is not known with certainty, but a possible explanation is an inhibition of VEGFR on the thyroid cells. Several studies have shown a longer survival in patients who develop hypothyroidism.

CTC AE grade

How to manage

Follow-up

Grade 1:
Asymptomatic or mild symptoms. TSH elevated (normal ref: 0.4–4.8 mI U/l), but < 10 and normal T4.

Grade 1:
Maintain TKI dose. No indication for intervention.

Grade 1:
Ask about symptoms of hypothyroidism: fatigue/lack of initiative, sensation of cold, weight increase, dry skin, hair loss, depression/change in personality, constipation, muscle/joint pain.

Grade 2:
TSH > 10 and/or low free T4 (reference interval different)

Grade 2:
Maintain TKI dose.
Initiate treatment with levothyroxine 50 micrograms x 1 (in the event of ischaemic heart disease 25 micrograms x 1).
The dose of levothyroxine will not be adjusted until after 6 weeks of treatment.

Grade 2:
After initiation of levothyroxine, TSH should be checked every 4–6 weeks.