Effects of thyroid hormone withdrawal on metabolic and cardiovascular parameters during radioactive iodine therapy in differentiated thyroid cancer

• Published in: Journal of international medical research Vol. 45; no. 1; pp. 38 - 50
• Main Authors: An, Jee Hyun, Song, Kee-Ho, Kim, Dong-Lim, Kim, Suk Kyeong
• Format: Journal Article
• Language: English
• Published: London, England SAGE Publications 01.02.2017
• Subjects: Adult; Blood Glucose - metabolism; C-Reactive Protein - metabolism; Cholesterol, HDL - blood; Cholesterol, LDL - blood; Cystatin C - blood; Drug Administration Schedule; Fasting - blood; Female; Fibrinogen - metabolism; Hormone Replacement Therapy - adverse effects; Hormone Replacement Therapy - methods; Humans; Hypothyroidism - blood; Hypothyroidism - etiology; Hypothyroidism - pathology; Insulin Resistance; Insulin-Secreting Cells - metabolism; Iodine Radioisotopes - therapeutic use; Male; Middle Aged; Prospective Studies; Research Reports; Thyroid Neoplasms - blood; Thyroid Neoplasms - pathology; Thyroid Neoplasms - radiotherapy; Thyroxine - therapeutic use; Treatment Outcome; Triglycerides - blood; atherosclerosis; metabolic syndrome; thyroid hormone withdrawal; thyroid cancer; Hypothyroidism
• ISSN: 0300-0605; 1473-2300
• DOI: 10.1177/0300060516664242

Objective To investigate the cardiometabolic effects of a severe hypothyroid state induced by withdrawal of thyroid hormone replacement before radioactive iodine therapy. Methods Patients with thyroid cancer who were scheduled to receive radioactive iodine ablation were enrolled. Cardiometabolic parameters were measured using blood samples taken immediately before levothyroxine withdrawal, 4 weeks following withdrawal (on radiotherapy day), and 4 weeks following reinstitution of levothyroxine. Results Out of 48 patients (age 49.4 ± 10.5 years; 77.1% [37/48] female), the severe hypothyroid state induced by levothyroxine withdrawal significantly aggravated the majority of lipid parameters, particularly in patients with a greater number of metabolic syndrome components. Fasting plasma glucose levels and homeostatic model assessment values for insulin resistance and β-cell function significantly decreased following levothyroxine withdrawal. Serum high-sensitivity C-reactive protein, fibrinogen and cystatin C levels significantly decreased, and homocysteine levels increased during the severe hypothyroid state. All of these changes were reversed by levothyroxine reinstitution. Conclusions Severe hypothyroid state induced pronounced changes in cardiometabolic parameters. Further studies should identify the long-term effects of changes in these parameters on cardiovascular morbidity and mortality in relation to thyroid disease.