Bone scintigraphy in acromegaly. Preliminary report on 10 cases.

The present study investigates if bone scintigraphy could be used as a diagnostic and prognostic tool in acromegaly. Bone scintigraphy (99m Tc-diphosphonate) was performed in 10 acromegalic (7 active and 3 inactive acromegaly) vs 12 control patients. Isotope uptake (in counts/cell) was assessed in the area of interest 3-4 hours after diphosphonate administration. Three views were chosen: cranium lateral (I)/frontal (II), and the hands (III). Between the acromegalic and control patients there were significant differences (x = p less than 0.001; xx = p less than 0.05) for the following areas: I-parietal: 66.5 vs 24.82x; I-occipital: 58.4 vs 23x; I-mediosphenoidal temporal: 55.2 vs 21.36x: I-nasal: 55.9 vs 38.73 xx; II-frontal: 46.8 vs 16.64 x; II-nasal: 59.8 vs 40.27 xx; III-left metacarpal: 21.67 vs 15.36 xx; III-right metacarpal: 21.78 vs 16.18 xx. Surprisingly, bone isotope uptake at the mandibular level, both in lateral and frontal view, showed no significant differences between acromegalic and control patients (55.2 vs 45 and 59.8 vs 44.5). Between the active and nonactive acromegalic patients there were no significant differences in any area. Bone scintigraphy, therefore, does not represent a useful index for disease activity. However, the results gave rise to two interesting problems: the acromegalic bone seems to have the same metabolic activity irrespective of the disease status; why is bone isotope uptake the same in acromegalics with pronounced prognathism as in the controls with normal mandible?