2.1 Participants
The study was approved by the Institutional Review Board and the Ethics Committee of our University Hospital with registration number EN18-00002. All participants provided informed consent before any study procedure.
We enrolled 54 participants: 18 with SCH (defined as a TSH > 4 µIU/ml and a normal free thyroxine level [0.7-1.55 ng/dl]); 18 with OH (defined as a TSH > 4 µIU/ml and a free thyroxine level < 0.7 ng/dl); and 18 HC. The inclusion criteria were subjects 18 years of age or older with untreated SCH, untreated OH, and HC recruited from the Endocrinology Division of the University Hospital. Participants were excluded if they had a past medical history of stroke, coronary artery disease, diabetes mellitus, malignancies, systemic lupus erythematosus (SLE), rheumatoid arthritis, smoking, or the use of medications that interfere with thyroid hormone measurements or function. The elimination criteria were subjects with SCH who discontinued the use of levothyroxine.