SERUM BONE GLA PROTEIN AND CARBOXYTERMINAL CROSS-LINKED TELOPEPTIDE OF TYPE-I COLLAGEN IN PATIENTS WITH CUSHINGS-SYNDROME

Serum bone Gla protein, a marker of bone formation, and carboxytermina l crosslinked telopeptide of type I collagen levels, an index of bone resorption, were evaluated in eight patients with active Cushing's syn drome and in four with 'preclinical' Cushing's syndrome, before and af ter surgery. In basal conditions, serum bone Gla protein levels were s ignificantly lower (p<0.0001) in patients with active Cushing's syndro me (1.0 +/- 0.35 ng/ml) than in controls (5.4 +/- 0.15 ng/ml); two out of four patients with the 'preclinical' form had reduced bone Gla pro tein levels, while in the other two cases levels were in the normal ra nge. Serum levels of carboxyterminal crosslinked telopeptide of type I collagen (3.0 +/- 0.4 ng/ml), although slightly reduced, were similar to those recorded in controls (4.1 +/- 0.3 ng/ml), both in patients w ith active and with preclinical Gushing's syndrome. After surgery seru m levels of both marker proteins significantly increased in seven out of eight patients with active Cushing's syndrome; in one patient, who was not cured after surgery, bone Gla proteins levels remained lower t han in normals, while levels of carboxyterminal cross-linked telopepti de of type I collagen had a transient increase after six months. In th e two patients with a 'preclinical' Cushing's syndrome who underwent s urgery, a significant rise of the levels of both marker proteins was o bserved, similar to that observed in patients with active Cushing's sy ndrome. It was concluded that serial determinations of these new marke rs of bone formation and resorption may be usefully employed to follow -up the clinical course of Cushing's syndrome and provide information on the rate of bone turnover in response to medical and/or surgical th erapies. Moreover, the evaluation of these markers in preclinical stat es of Cushing's syndrome might suggest the need for surgery.