Late onset hypothyroidism after subtotal thyroidectomy for hyperthyroidism: implications for long term follow-up

Area of Science:

• Endocrinology
• Surgical Oncology
• Thyroidology

Background:

• Subtotal thyroidectomy for hyperthyroidism can lead to hypothyroidism.
• Early and late onset hypothyroidism are known complications.

Purpose of the Study:

• To record and analyze the incidence of early and late onset hypothyroidism in post-thyroidectomy patients.
• To assess the long-term risk of hypothyroidism after subtotal thyroidectomy for hyperthyroidism.

Main Methods:

• A follow-up register was used in Aberdeen and Dundee.
• Prospective study over 12 years involving euthyroid patients post-surgery.
• Actuarial methods were employed to estimate incidence rates.

Main Results:

• Prevalence of postoperative hypothyroidism was 41% at register entry in one center (1170 patients).
• 93% of early hypothyroidism cases occurred within 18 months.
• 10-year incidence was 7.4% in one center (683 patients) and 5-year incidence was 10.8% in another (156 patients).
• Minimum predicted annual incidence is 1%.

Conclusions:

• Hypothyroidism after subtotal thyroidectomy for hyperthyroidism presents a bimodal pattern.
• Large thyroid remnants do not prevent hypothyroidism but increase recurrent hyperthyroidism risk.
• Continuous, lifelong follow-up is essential for patients undergoing thyroidectomy.