Reduction of lung distensibility in acromegaly after suppression of growthhormone hypersecretion

Whether the growth of the lungs in acromegaly is due to alveolar hypertroph y or alveolar hyperplasia is a subject of debate. To discriminate these hyp otheses, we compared pulmonary distensibility and diffusing capacity among 11 patients with active acromegaly and 11 matched control subjects, evaluat ing the response of pulmonary distensibility and diffusing capacity to supp ression of growth hormone (GH) hypersecretion. We performed lineal and expo nential analyses of quasistatic pressure-volume curves. Patients with activ e acromegaly had a greater TLC, lung compliance, and shape constant, K, tha n did normal subjects. We found no significant differences between the stud y groups in carbon monoxide diffusing capacity or diffusing capacity per un it of alveolar volume. After treatment, patients with inactive acromegaly s howed a reduced TLC (6.95 +/- 1.40 [mean +/- SD] L versus 6.35 +/- 1.23 L), reduced lung compliance (3.61 +/- 0.90 L/kPa versus 2.36 +/- 0.79 L/kPa), reduced K coefficient (2.62 +/- 0.65 kPa(-1) versus 1.35 +/- 0.40 kPa(-1)), and increased maximal recoil pressure (1.74 +/- 0.38 kPa versus 2.28 +/- 0 .25 kPa). We conclude that the increased lung distensibility with normal di ffusion capacity demonstrated in patients with active acromegaly, which was partly reversible after suppression of GH hypersecretion, suggests that lu ng growth in acromegaly may result from an increase in alveolar size.