The criteria for biochemical control of
acromegaly that will best reduce disease-related morbidity in
acromegaly are debated. We therefore studied the relationship of
biochemical markers with an important metabolic parameter,
insulin sensitivity, and clinical parameters reflecting disease activity in
acromegaly. Newly diagnosed and postoperative patients with
acromegaly underwent assessment of fasting
IGF-I and fasting and postoral
glucose tolerance test GH and
insulin levels and completed a numeric signs and symptoms questionnaire.
Insulin sensitivity was estimated by the quantitative
insulin sensitivity check index (QUICKI) and the composite
insulin sensitivity index. Patients were divided into three groups: group I, normal
IGF-I and nadir GH less than 0.14 mug/liter (n = 21); group II, normal
IGF-I and nadir GH 0.14 mug/liter or more (n = 20); group III (active), elevated
IGF-I (n = 25). Age, sex, and body mass index were comparable in these groups.
Insulin sensitivity was reduced in group III (QUICKI: 0.33 +/- 0.01 and composite index: 3.44 +/- 0.54), compared with group II (0.38 +/- 0.01, P = 0.002 and 8.18 +/- 1.21, P = 0.0008), group I (0.38 +/- 0.01, P = 0.0008 and 8.91 +/- 1.34, P = 0.00001), and healthy controls (0.37 +/- 0.008, P = 0.009). When other nadir GH cut-offs were analyzed,
insulin sensitivity remained relatively reduced in the elevated
IGF-I group.
IGF-I was a significant predictor for decreasing
insulin sensitivity as calculated by QUICKI (r = 0.6, P < 0.0001) independently of nadir GH. Signs and symptom scores were higher in group III (mean 38.5 +/- 3.6%), compared with group II (mean 23.5 +/- 3.2%, P = 0.004) and group I (mean 20.5 +/- 3.7%, P = 0.0008) but not between the latter two groups. Our data indicate that overall and specifically in the presence of discordant serum
IGF-I and nadir GH levels,
IGF-I was more predictive than GH levels of
insulin sensitivity and clinical symptom score in patients with
acromegaly.