29
Table 4. Endocrine Toxicities
G2: Moderate symptoms,
able to perform ADL. TSH
persistently >10 mIU/L
• May continue or hold ICPi until symptoms resolve
to baseline.
• Consider endocrine consultation for unusual clinical
presentations, concern for central hypothyroidism,
or difficulty titrating hormone therapy.
• Prescribe thyroid hormone supplementation in
symptomatic patients with any degree of TSH
elevation or in asymptomatic patients with TSH
levels that persist over 10 mIU/L (measured 4 weeks
apart).
• Monitor TSH every 6–8 weeks while titrating
hormone replacement to goal of TSH within the
reference range.
• FT4 can be used to help interpret ongoing abnormal
TSH levels on therapy, as TSH may take longer to
normalize.
• Once adequately treated, repeat testing every 6–12
months or as indicated for a change in symptoms.
G3–4: Severe symptoms,
medically significant or life-
threatening consequences,
unable to perform ADL
• Hold ICPi until symptoms resolve to baseline with
appropriate supplementation
• Endocrine consultation to assist with rapid
hormone replacement.
• Hospital admission for developing myxedema
(bradycardia, hypothermia, altered mental status).
• Inpatient endocrinolog y consultation can assist
with IV levothyroxine dosing, steroids, and
supportive care.
• If there is uncertainty about whether primary or
central hypothyroidism is present, hydrocortisone
should be given before thyroid hormone is initiated.
• Myxedema coma is a life-threatening emergency
requiring admission and a high level of care.
• Thyroid supplementation and reassessment as in G2.
Additional considerations:
• For patients without risk factors (i.e., <70 years old, not frail, and without cardiac
disease or multiple comorbidities), full replacement can be estimated using ideal-
body-weight for a dose of approximately 1.6 mcg/kg/day.
• For those over age 70 and/or frail patients with multiple comorbidities (including
cardiac disease), consider titrating up from a lower starting dose of 25–50 mcg.
• Elevated TSH can be seen in the recovery phase of thyroiditis. In asymptomatic
patients with FT4 that remains in the reference range, it is an option to monitor
before treating to determine whether there is recovery to normal within 3–4 weeks.
Progression or development of symptoms should be treated as per G2.
• Development of a low TSH on therapy suggests over-treatment or recovery of thyroid
function and dose should be reduced or discontinued with close follow up.
