SFEBES2007 Poster Presentations Bone (16 abstracts)
Differences in parathyroid hormone secretory rhythm and sensitivity in aging women with osteoporosis and declining insulin like growth factor-1 concentration, compared to young healthy premenopausal women
Franklin Joseph 1 , Aftab M Ahmad 1 , Ashwin Joshi 1 , Amar Wakil 1 , Brian H Durham 2 , Pauline Whittingham 1 , William D Fraser 2 & Jiten P Vora 1
1Department of Diabetes and Endocrinology, Royal Liverpool University Hospital, Liverpool, United Kingdom; 2Department of Clinical Biochemistry, Royal Liverpool University Hospital, Liverpool, United Kingdom.
Introduction: Adult growth hormone deficiency (AGHD) is associated with target organ insensitivity to parathyroid hormone (PTH) and abnormal PTH circadian rhythm. In aging women with established osteoporosis, GH and insulin like growth factor -1 (IGF-1) concentrations are low and administration of GH has been shown to increase bone turnover and bone mineral density (BMD), but the mechanisms remain unclear. Consequently we investigated the effects of declining GH and IGF-1 concentrations on PTH sensitivity and PTH circadian rhythm in aging women with established osteoporosis.
Methods: Following ethical approval 14 women with osteoporosis (mean±S.E.M.: 63.4±2.1 years) were compared with 14 healthy young premenopausal control women (33.9±2.2 years). PTH, IGF-1 and nephrogenous cyclic AMP (NcAMP) were measured from half-hourly blood and 3-hourly urine samples. Circadian rhythm parameters of PTH (midline estimate statistic of rhythm (MESOR), acrophase and amplitude) was performed using Chronolab 3.0. Student’s ‘t’ test for unpaired data was used to determine differences between groups.
Results: IGF-I concentration was significantly lower in the aging women with established osteoporosis as compared to the young controls (102.8±10.0 μg/L versus 140.9±10.8 μg/L; P<0.05). 24-h mean PTH concentration was higher in the osteoporotic women (5.41±0.08 pmol/L) than in healthy young controls (4.37±0.08 pmol/L, P<0.001). NcAMP was significantly lower in osteoporotic women (16.99±1.26 nmol/L GFR) as compare to controls (21.37±1.42 nmol/L GFR, P<0.05). All subjects demonstrated significant PTH circadian rhythms (P<0.001) but with differences between patients and controls. The mean PTH MESOR was significantly higher in the osteoporotic women than in the controls (5.42±0.33 pmol/L versus 4.38±0.33 pmol/L, P<0.05), but there was no significant difference in the amplitude or acrophase.
Conclusion: Aging women with osteoporosis have lower circulating IGF-1 concentration which may contribute to PTH resistance and abnormal PTH circadian rhythm, which may in turn contribute to the development of osteoporosis.
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Endocrine Abstracts
ISSN 1470-3947 (print) | ISSN 1479-6848 (online)
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