Context: Patients with active acromegaly have increased bone turnover and skeletal abnormalities. Biochemical cure of acromegaly may represent a functional GH deficient state and result in cortical bone loss. Reduced PTH target-organ sensitivity occurs in adult GH deficiency and may underlie the associated development of osteoporosis.

Objective: We examined the effect of active and treated acromegaly on PTH concentration and target-organ sensitivity.

Patients: 10 active acromegalics (GH nadir >0.3µ/L following 75 g oral glucose load and IGF1 above age-related reference range) and 10 matched controls.

Design: -hourly blood and 3-hourly urine samples were collected on patients and controls for 24 h. Samples were analyzed for PTH, calcium (Ca), nephrogenous cyclic AMP (NcAMP, marker of PTH renal activity), CTX (bone resorption marker) and PINP (bone formation marker). 8 acromegalics who achieved biochemical cure (GH nadir <0.3µ/L following 75 g oral glucose load and IGF1 within reference range) following standard surgical and/or medical treatment re-attended and the protocol repeated.

Results: Active acromegalics had higher 24 h-mean PTH, NcAMP, serum adjusted Ca, urine Ca, CTX and PINP (P < 0.05) compared with controls. 24 h-mean PTH increased (P < 0.001) in the acromegalics following treatment, while NcAMP and ACa decreased (P < 0.05).

Conclusion: Increased bone turnover associated with active acromegaly may result from increased PTH concentration and action. Biochemical cure of acromegaly results in reduced PTH target-organ sensitivity indicated by increased PTH with decreased NcAMP and ACa concentrations. PTH target-organ sensitivity does not appear to return to normal following successful treatment of acromegaly in the short-term, and may reflect functional GH deficiency.