PTH and rheumatoid arthritis: We aim to evaluate the rule of chronic heavy metals toxicity on the induction of vitamin D3 (VD) deficiency and parathyroid hormone (PTH) disturbances in an inflammatory disease like rheumatoid arthritis (RA) and non-inflammatory disease like fibromyalgia syndrome (FMS).<h4>Methods</h4>This comparative analytical study was conducted on sixty adults (age ≥ 18 years).