Norepinephrine activity, as measured by MHPG, is associated with menopausal hot flushes

Abstract

Objectives Baseline norepinephrine levels, as measured by a metabolite (plasma 3-methoxy-4-hydroxyphenolglycol, MHPG), have been reported to increase in women who experience hot flushes. However, norepinephrine is also discharged in a counter-regulatory attempt to increase brain glucose as normal daily variations occur. The purpose of this analysis is to examine the relationship between hot flush frequency and MHPG under conditions of experimental glucose manipulation.

Methods A repeated-measures experimental design study was conducted with ten postmenopausal women taking hormone therapy between the ages of 38 and 55 years. In a 30-h experimental protocol, participants received normal saline and 20% glucose intravenous infusions on sequential days and were monitored for hot flushes and blood glucose changes. MHPG levels were evaluated before and after each experimental condition as a biomarker of norepinephrine activity.

Results Although hot flush frequency was significantly different between infusion periods, mean MHPG levels were not statistically different (normal saline period, 3.1 ng/ml; glucose infusion, 3.2 ng/ml). No distinct patterns of MHPG change were found in this sample.

Conclusions In this study, there was no consistent pattern of MHPG increase or decrease in the women experiencing hot flushes.

Key words:

• HOT FLUSHES
• MHPG
• GLUCOSE
• NOREPINEPHRINE
• MENOPAUSE