The factors that determine the course of the disease in asymptomatic primary hyperparathyroidism cases

Primary hyperparathyroidism (PHPT) is characterized most commonly as an asymptomatic disorder with excessive secretion of parathyroid hormone from the parathyroid glands. Data are lacking regarding the natural history of asymptomatic variant of PHPT. PHPT is a disorder that primarily influences the bone metabolism. However experimental studies showed that PHPT may promote insulin resistance (IR), insulin defficiency and overt diabetes mellitus (DM) in long term. In our study, we aimed to evaluate the natural history of the bone metabolism and IR in the asymptomatic PHPT patients for 18 months. We administered a 75g oral glucose tolerance test to 61 asymptomatic PHPT patients who admitted to our policlinic and assessed the IR index of them. The natural history of these parameters were evaluated in every 6 months for 18 months. Bone metabolism of these patients were also evaluated by bone mineral density (BMD) changes in time. The collected data were compared with the healthy control group (n=80). Although demographical, clinical and biochemical characteristics were similar in both groups, increase in the prevalence of high fasting insulin concentration (p=0.031) and IR (p=0.035) was found in asymptomatic PHPT. At the 18th month, there was a statistically significant increase in the prevalence of high fasting insulin concentration and IR but it was not different from the 0th month. The prevalence of impaired fasting glucose (IFG) was 11.5% in the PHPT group and 9.8% in the control group but the difference did not reach statistical significance. The prevalence of DM were the same in both of the groups. The positive familial history of DM, IFG, IGT were seen in both groups but overall the proportion of first degree DM relatives was found to be lower in the PHPT group than the control group (p=0.032). Although there was no genetical predisposition, the risk of IR was higher in the PHPT group. Comparison of the biochemical data at the beginning and end of the study revealed a significant increase in the PTH levels in the PHPT patients (p=0.043), while the serum levels of calcium, phosphorus and 24 h urine calcium, phosphorus levels did not differ. When we compared the bone mineral densities of the PHPT group at the 6th, 12th, 18th months, there was a significant increase in the femur neck (p=0.020) and the trochanter (p=0.028) densities but there was no change in the BMD values at distal 1/3 radius and lumber spine at the 18th month. Further researches are required to find out the metabolic consequences of asymptomatic PHPT and thus able to make a consensus about the rational management to treat and follow up these patients. Until that time it is advisable to evaluate the nonoperated PHPT patients in detail with regard to bone metabolism as well as the glucose metabolism for the possible risk of developing ID and DM.