IRON PROFILE, VITAMIN B12 STATUS AND SERUM LACTATE DEHYDROGENASE IN HYPOTHYROIDISM AND THEIR CORRELATION WITH THYROID FUNCTION: A CROSS-SECTIONAL STUDY

Abstract

Background: The systemic effects of hypothyroidism extend beyond the thyroid axis to iron handling, vitamin B12 status and markers of cellular and muscle stress such as lactate dehydrogenase (LDH). Most published work has examined these parameters separately rather than together. Objective: To evaluate iron status, LDH activity and vitamin B12 levels in patients with hypothyroidism and to examine their association with thyroid function. Methods: A single-centre, laboratory-based, cross-sectional observational study was conducted over 18 months in the Department of Biochemistry of a tertiary teaching hospital in Rewa, Madhya Pradesh. One hundred and fifty-five patients with hypothyroidism aged 18-60 years were enrolled by convenience sampling from the outpatient and inpatient departments. Free T3, free T4 and thyroid-stimulating hormone (TSH) were measured by chemiluminescent immunoassay, and serum iron, ferritin, total iron-binding capacity (TIBC), LDH and vitamin B12 by standard automated methods. Normality was assessed by the Shapiro-Wilk test and associations by Pearson correlation, with significance set at p < 0.05. Results: Mean age was 45.33 ± 8.96 years (67 men, 88 women). Mean free T3 was 2.21 ± 0.18 pg/mL, free T4 0.61 ± 0.07 ng/dL and TSH 13.27 ± 2.38 µIU/mL. Serum iron (47.93 ± 4.33 µg/dL) and ferritin (24.14 ± 3.59 ng/mL) were low with elevated TIBC (399.58 ± 16.04 µg/dL); LDH was raised (276.05 ± 14.96 U/L), vitamin B12 was low (168.94 ± 15.65 pg/mL) and haemoglobin indicated mild anaemia (11.21 ± 0.55 g/dL). TSH correlated negatively with iron (r = −0.76), ferritin (r = −0.84), vitamin B12 (r = −0.66) and haemoglobin (r = −0.43), and positively with TIBC (r = 0.74) and LDH (r = 0.57; all p < 0.001); free T3 and free T4 showed the mirror-image pattern. Neither white cell count nor red cell count correlated with thyroid function, and platelet count showed only a weak association with free T4. Conclusion: In this cohort hypothyroidism was accompanied by a consistent pattern of iron depletion, vitamin B12 depletion, raised LDH and mild anaemia, each correlating with the degree of thyroid dysfunction. The findings support assessment of iron and vitamin B12 status, alongside LDH, in the clinical evaluation of hypothyroid patients, although a cross-sectional design without a euthyroid comparison group cannot establish causal direction.