Abstract:

Background: The Thyroid gland is very crucial to overall health, and its derailment may trigger a host of health complications. These disruptions can be caused internally or by an external stimulant that stimulates a pathway to the end result of either destroying the gland or to increase the activity of the gland. Prolonged stress on the thyroid caused by chronic use of heavy metals may cause damage to the gland by developing antibodies against the thyroid; this process is central in the development of autoimmune thyroid disease.

The Purpose of the Investigation: To research the role and influence of some heavy metals, i.e., cadmium, lead, chromium, zinc, and copper, on the status of thyroid glands, and to determine whether the routine analysis of these metals is reasonable in case of thyroid dysfunction.

Subjects, Materials, and Methods: 30 healthy controls, 30 patients with hyperthyroidism, and 30 patients with hypothyroidism were enlisted as subjects. All subjects were between the ages of 25 and 65 years of age, and the sample had 24 females and eight males in each group. This was done through clinical and laboratory tests. Laboratory tests included the determination of S.TSH, Total S.T3, and Total S.T4 (at the visits of patients to the Specialized Center of Endocrinology and Diabetes and Al-Sadr General Hospital), and the first values were taken based on the archival medical histories. These tests used enzyme-linked fluorescent immunoassay (ELFA); S.TPO concentration was measured through enzyme-linked immunosorbent assay (ELISA). Flame Atomic Absorption Spectrophotometry (FAAS) and Graphite Furnace Atomic Absorption Spectrophotometry (GFAAS) were used to determine the content of metal (lead, cadmium, chromium, copper, and zinc) levels in serum. The research was performed between the months of November 2020 and January 2021.

Findings: It was found that both hypo- and hyperthyroid patients had a high level of lead, cadmium, and copper ( p < 0.05) and significantly lower levels of chromium and zinc ( p < 0.05) in comparison with healthy controls. The results showed that in hyperthyroid patients, TSH was negatively correlated with lead (r=-0.41, p=0.05) and cadmium (r=-0.56, p=0.05), and no correlation was observed between TSH and lead, cadmium, chromium, copper, and zinc in hypothyroidism. The results in both hypo- and hyperthyroid groups showed no significant relationship (p < 0.05) between thyroid hormones (T3 and T4) or TPO-Ab and the above heavy metals.

Conclusion: We could suggest that the dysfunction of the thyroid gland, be it hypothyroidism or hyperthyroidism, is connected to the changes in the levels of heavy metals (Pb, Cd, Cr, Cu, Zn); some of them are increased (Pb, Cd, Cu), and some of them are reduced (Cr, Zn). These results can be supported by comparative studies against healthy subjects. Nevertheless, the research cannot conclusively identify a causal relationship or a particular mineral change to either thyroid disease, other than probably Cd. Therefore, it is necessary to investigate more specific research and conduct bigger studies in order to consider routine heavy metal evaluation in patients with thyroid dysfunction.