Understanding Thyroiditis: The Link Between Cyto-Morphological and Biochemical Parameters

Background: The thyroid gland is the primary endocrine organ responsible for the production of thyroxine (T4) and triiodothyronine (T3), which regulate metabolic activity. Vitamin D is essential for calcium homeostasis and immune modulation, with deficiencies implicated in autoimmune thyroid disease (AITD). Excessive iodine intake is also associated with increased risk of thyroid dysfunction. This study aimed to evaluate clinical, biochemical, and cyto-morphological features of thyroid disorders, with a focus on autoimmune thyroiditis, and to analyze the relationship between thyroid hormone status, vitamin D levels, urinary iodine concentration, and cytological patterns. Methods: A prospective observational study was conducted over 18 months at Dr. D. Y. Patil Medical College, Pune, involving 50 adult patients with clinically suspected AITD. Exclusion criteria included pediatric age, pregnancy, and lactation. Fine-needle aspiration cytology (FNAC) was performed on thyroid lesions, with smears stained using hematoxylin and eosin. Biochemical investigations included thyroid function tests (TSH, fT3, fT4), anti-thyroid peroxidase antibody (TPOAb) assays, serum vitamin D estimation, and urinary iodine analysis via UV spectrophotometry. Results: Participants were predominantly in the 41–50-year age group with near-equal gender distribution. The most common presenting symptoms were neck pain (26%) and hoarseness (24%). Hypothyroidism was the most frequently observed clinical diagnosis (46%). FNAC revealed follicular hyperplasia and lymphocytic thyroiditis in 34% of cases. Biochemically, the mean TSH was 4.545 mIU/L. Sufficient vitamin D levels were observed in 54% of participants, while 42% had elevated urinary iodine levels. Significant associations were noted between: • Vitamin D and thyroid hormone status (p = 0.03), and follicular hyperplasia (p = 0.009) • Urinary iodine and thyroid hormone status (p = 0.028), and lymphocytic thyroiditis (p = 0.030) However, correlations between TPOAb, vitamin D, and urinary iodine levels were weak and statistically non-significant. Conclusion: Vitamin D and urinary iodine levels demonstrate significant associations with thyroid hormone status and specific cytological patterns in thyroiditis, supporting their potential utility in diagnostic evaluation and disease management. While elevated TPOAb levels remain a diagnostic hallmark of AITD, they do not strongly correlate with other biochemical parameters, underscoring the multifactorial nature of thyroid pathophysiology.