Context: The pulsatility of GH secretion in acromegaly poses difficulty in ascertaining true daily GH milieu in patients with this disease. Intensive GH sampling (Q10–20 min for 24h) is not practical in clinical practice.

Objective: To ascertain reliability of abbreviated sampling protocols to reflect true 24h mean GH concentrations in patients with acromegaly.

Design: Analysis of previously-obtained plasma GH profiles

Setting: General Clinical Research Center at the University of Michigan

Patients: A total of 115 GH profiles obtained in 94 patients with active acromegaly.

Intervention: Frequent blood sampling, i.e. Q10–20 min for 24h.

Main Outcome Measure: Concordance of 24h mean GH concentrations derived from Q10–20 min samplings with abbreviated GH sampling schedules. The study was planned after data collection.

Results: All abbreviated schedules of GH sampling correlated well with the true 24h plasma GH means (i.e. Q10–20 min sampling), R = 0.93–0.98; p < 0.0001 for all. In the GH range > 20 µg/L, only 5h and 9h means had R values > 0.9. Single GH concentrations < 1 µg/L had PPV of only 0.29 and those with < 2.5 µg/L had PPV of 0.67 vs. their corresponding 24h mean GH values of the same magnitude.

Conclusions: The intensity of GH sampling in patients with acromegaly may vary depending on the nature of the required information. Investigators and clinicians should be aware of the limitations of the abbreviated GH sampling protocols in acromegaly.