Endocrine Abstracts

Introduction: Acromegaly is associated with skeletal changes that are characterized by appositional bone growth, increased bone dimensions and increased bone turnover. PTH is an important regulator of bone remodeling and its anabolic action requires the presence of GH. The strong correlation found between PTH concentrations and bone turnover markers in active and treated acromegaly has led to the suggestion, that the effect of GH on bone turnover may be mediated by PTH. Successful treatment of acromegaly results in a reduction of bone turnover markers but previous reports on the effect of PTH concentrations have been inconsistent. The aim of the present study was to evaluate parathyroid function in patients with acromegaly after surgical treatment.

Patients and methods: We studied 47 acromegalic patients (27 females and 20 males) aged 62+8 who were treated with transphenoidal surgery. Serum concentrations of IGF-1, iPTH, calcium, phosphorus, alkaline phosphatase, creatinine and albumin as well as 24 h urinary calcium and creatinine were measured. Patients were divided in 3 groups according to GH levels after an oral glucose tolerance test with 100 g glucose: group A 18 patients (11F-7M) with GH<1 ng/ml, group B 17 patients (10F-7M) with GH between 2 and 10 ng/ml and group C 12 patients (6F-6M)with GH>10 ng/ml.

One way analysis of variance (ANOVA) was used for comparisons between the three groups and correlations were sought using Pearsons correlation coefficient.

Results: As expected, GH and IGF-1 levels were significantly different between the three groups of patients (P<0.001). iPTH levels did not differ between groups and no correlation was found with any of the measured variables. Serum calcium, phosphorus and alkaline phosphatase levels were not different between groups while 24 h urinary calcium was significantly higher in group B compared to patients in group A (250.2±22.4 vs 184.4±21.4, P<0.04). In all patients, a positive correlation was found between serum calcium with GH and IGF-1 levels (r=0.33, P<0.05 and r=0.35, P<0.05 respectively) and alkaline phosphatase with IGF-1 levels (r=0.4, P<0.02).

Conclusions: In active acromegaly, parathyroid function as expressed by iPTH levels does not seem to be influenced while the augmented levels of GH and IGF-1, have a positive effect on bone metabolism via the increased calcium intestine absorption on one hand and the increased osteoblastic activity on the other.