Endocrine Abstracts

Introduction: Cardiovascular complications are the most relevant cause of mortality in patients with acromegaly.

Aims: To evaluate the association of diurnal melatonin profile with arterial hypertension in acromegalic patients.

Subjects and methods: Thirty seven patients (15 men and 22 women; aged 18–75 years) with acromegaly were under investigation. Blood samples for GH and, IGF1 were taken in fasting state. 6-Sulfatoxymelatonin (6-SMT), the main melatonin metabolite, was determined by fluorometric assay by C. Druex in two separated urine portions: in the daytime (6-SMTd) and nighttime (6-SMTn). Routine measurements of blood pressure (BP) were done. The average of three measurements with a mercury sphygmomanometer was used in all analysis. The BP varied in large SBP (80–176 mm/Hg); DBP (58–116 mm/Hg). Arterial hypertension (AH) was diagnosed when BP was above 140/90 mm/Hg. Disease activity was evaluated according to the Consensus Conference criteria (2000). Data are given as mean±S.E.M. and nonlinear regression model equations parameters.

Results: In patients with somatotropinoma (GH, 22.8±3.5 ng/ml) and somatomamotropinoma (GH, 26.3±5.3 ng/ml) the diurnal level of 6-SMT (96.5±9.8 nmol) including 6-SMTn (46.8±5.6 nmol) and 6-SMTd (49.7±5.6 nmol), 6-SMTd/6-SMTn (1.46±0.22) have been found out. It was revealed that in patient without AH the modulating action of melatonin on DBP is approximated by equations: DBP≈48.2+7.2×ln (6-SMTn) (R²=37.9%; r=0.61; P=0.02). In patient with AH the negative associations exist between level of 6-SMTn and SBP (R²=27.8%; r=−0.52; P=0.01), and 6-SMTn and DBP (R²=47.8%; r=−0.69; P=0.004). The 90% of patient with AH have the diurnal level of 6-SMT <120 nmol including 6-SMTn <80 nmol and 6-SMTd <40 nmol.

Conclusion: In patients with active acromegaly AH is associated with 6-SMT<120 nmol and 6-SMTd/6-SMTn >1. For hypertensive patients with acromegaly decreased level of melatonin in nighttime is more appropriate than in daytime. Altered diurnal profile of melatonin may be one of the cause of AH in patients with acromegaly.