Prevalence of endogenous normal thyroid function 3 years after hemithyroidectomy for differentiated thyroid cancer

Area of Science:

• Endocrinology
• Oncology

Background:

• Differentiated thyroid cancer (DTC) management often involves hemithyroidectomy.
• Postoperative management strategies aim to maintain thyroid function and prevent recurrence.

Purpose of the Study:

• To determine the prevalence of normal endogenous thyroid function three years after hemithyroidectomy for low-risk DTC.
• To assess the impact of accepting a postoperative thyroid stimulating hormone (TSH) level up to 4 mIU/L on the need for levothyroxine replacement therapy.

Main Methods:

• Retrospective review of 162 Eastern Danish patients treated for DTC.
• Patients were followed without levothyroxine if postoperative TSH was below 4 mIU/L.
• Data collected included levothyroxine initiation, TSH levels, recurrence, and remnant lobe nodularity.

Main Results:

• 88% of patients did not require levothyroxine pre-surgery.
• Endogenous normal thyroid function decreased from 80% at one year to 66% at three years post-hemithyroidectomy.
• Hypothyroidism (TSH >4.0 mIU/L) developed in 34% of patients by three years, necessitating levothyroxine treatment.
• In patients not on levothyroxine, TSH levels significantly increased within the normal range over three years (p<0.0001).
• No recurrence was observed; 3% underwent completion thyroidectomy due to nodule growth.

Conclusions:

• Approximately one-third of DTC patients require levothyroxine treatment three years post-hemithyroidectomy when a TSH threshold of 4 mIU/L is accepted.
• Avoiding levothyroxine treatment in this cohort leads to a significant increase in TSH levels.