Background: Hypothyroidism is one of the most common forms of hormonal dysfunction resulting from deficiency of thyroid hormone or its impaired activity. Various electrolyte and mineral disturbances have been observed in many studies. The role of thyroid hormones on mineral metabolism and its complications have not been established. Objective: To assess the alterations in the levels of serum magnesium, calcium and phosphorous levels in subclinical hypothyroidism. Materials and Methods: A descriptive case control study was done with a total 100 subjects in the department of Internal Medicine, Rangpur Medical College Hospital, Rangpur, Bangladesh from January 2008 to December 2008. 25 subclinical hypothyroidism cases, 25 overt hypothyroidism cases and 50 controls were taken. Blood sample for analyzing serum free T3, free T4, TSH, calcium, magnesium and phosphorus was taken and estimated in all subjects. Results: In this study the mean age of hypothyroidism (subclinical and overt) cases was 35.46 ± 7.26. A significant hypocalcaemia (P = 0.002) was observed in cases with overt hypothyroidism and a significant (P = 0.01) hyperphosphatemia was observed in cases with subclinical hypothyroidism. Conclusion: The present study showed a significant hypocalcaemia in overt hypothyroidism cases than controls and showed significant hyperphosphatemia in subclinical hypothyroidism. It can be concluded that there are various electrolyte disturbances in both subclinical and overt hypothyroidism, hence such disturbances need to be monitored prospectively to avoid further complications and needs to be treated accordingly.