Category: Pituitary Disorders/Neuroendocrinology

Monitor: 30

30 - INSULIN SECRETION DOES NOT COMPENSATE FOR REDUCED INSULIN SENSITIVITY IN PATIENTS WITH ACTIVE ACROMEGALY AND ABNORMAL GLUCOSE TOLERANCE

Thursday, Apr 25
11:00 AM – 11:30 AM

Objective :

Reduced insulin sensitivity (ISen) is a well-known feature of active acromegaly but insulin secretion (ISec) has been far less studied. Also, the relative contribution of ISen and ISec to abnormal glucose tolerance in patients with acromegaly is unclear. Our objective was to assess ISen and ISec in patients with active acromegaly and normal or abnormal glucose tolerance.


Methods :

We performed an intravenous glucose tolerance test (IVGTT) in 13 patients with active acromegaly (8 with normal glucose tolerance [NGT], 3 with diabetes mellitus [DM] and 2 with impaired fasting glucose [IFG]) and 3 healthy controls. For IVGTT a glucose dose of 0.3 g/kg of body weight was administered in 1 min time. Blood was sampeled thereafter at 0, 2, 3, 4, 5, 6, 8, 10, 15, 20, 25, 30, 40, 50, 60, 75 min after glucose infusion for measurement of serum insulin and glucose levels. ISen was calculated as kG * 106/AUCins, were kG is the rate of glucose elimination form the blood, and AUCins is the area under the curve of serum insulin between 0 and 75 min after glucose infusion and is measured in L/(pmol * min2). ISec was calculated as the acute insulin response, the ΔAUCins (above baseline) between 2 and 10 min after glucose infusion and is measured in pmol/L * min. Disposition index (DI) was calculated as ISen * ISec.


Results : ISen was significantly reduced in patients with active acromegaly (1.04±0.63 in NGT and 0.94±0.81 in IFG+DM) compared with healthy controls (5.0±4.4; p<0.05). ISec was significantly higher in NGT patients (3464±712) compared with patients with abnormal glucose tolerance (DM+IFG) (1028±1600) and healthy controls (1583±723). DI was higher in healthy controls (5837±1894) than in NGT patients (3685±2544). Patients with abonormal glucose tolerance (DM+IFG) had significantly lower DI (334±366) than NGT patients.


Discussion : To our knowledge this is the first IVGTT study for assessing ISen and ISec in patients with acromegaly. Similar to other studies with different methodology we found that patients with active acromegaly have reduced ISen compared with healthy controls. ISen is preserved in patients with NGT but is is usually severely diminished in patients with DM or IFG. DI shows that in patients with abnormal glucose tolerance ISen does not compensate for the reduces ISen.


Conclusion : ISen is reduced in active acromegaly. However, for abnormal glucose tolerance inadequate ISec is needed.

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Dan A. Niculescu

Assistant Lecturer
Department of Endocrinology, Carol Davila University of Medicine and Pharmacy, Bucharest, Romania
Bucharest, Bucuresti, Romania

NA

Roxana Dusceac

Assistant Lecturer
Department of Endocrinology, Carol Davila University of Medicine and Pharmacy, Bucharest, Romania

NA

Andra Caragheorgheopol

Senior Resercher
Research Laboratory, C. I. Parhon National Institute of Endocrinology, Bucharest, Romania

NA

Nicoleta Popescu

Chemist
Medical Laboratory, C. I. Parhon National Institute of Endocrinology, Bucharest, Romania

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Catalina Poiana

Professor of Endocrinology
Department of Endocrinology, Carol Davila University of Medicine and Pharmacy, Bucharest, Romania

NA