Journal of Clinical Endocrinology & Metabolism, Vol 72, 69-76, Copyright © 1991 by Endocrine Society

ARTICLES

Circadian variation in ionized calcium and intact parathyroid hormone: evidence for sex differences in calcium homeostasis

MS Calvo, R Eastell, KP Offord, EJ Bergstralh and MF Burritt
Division of Endocrinology, Metabolism, and Internal Medicine, Mayo Clinic, Rochester, Minnesota 55905.

The rate of bone loss with age and the incidence of osteoporosis are greater in women than men, which led us to question whether subtle sex differences may occur in the circadian variation of serum ionized calcium (iCa) and PTH. We measured iCa hourly and intact PTH every 2 h for 26 h in 25 women (21-69 yr) and 24 men (20-67 yr) consuming self- selected diets. Urine was collected at 0800-1600, 1600-2400, and 2400- 0800 h. Serum iCa levels followed a circadian rhythm in both sexes (P less than or equal to 0.01), and the patterns differed between sexes, notably during early morning, when serum iCa levels were lower in women (P = 0.02). Urinary calcium excretion and fractional excretion of calcium declined in both sexes at night (2400-0800 h), but the decline in men was significantly greater (P = 0.02). Similarly, the percent reduction in urinary calcium excretion at night was greater in men than in women (34% vs. 17%; P less than or equal to 0.05). In women, 26-h mean serum iCa values correlated significantly with total daily calcium intake (r = 0.44; P = 0.03). Serum intact PTH levels showed a significant circadian pattern in both sexes (P less than or equal to 0.001). The patterns of serum intact PTH differed between the sexes (P = 0.05), with an earlier and greater increase at night in men. This blunted nocturnal rise in PTH in women may explain the poor nocturnal adaptation to fasting found in women who, despite lower calcium intake, did not reduce urinary calcium loss at night as effectively as men.

This article has been cited by other articles:

				H. D. White, A. M. Ahmad, B. H. Durham, S. Chandran, A. Patwala, W. D. Fraser, and J. P. Vora Effect of Active Acromegaly and Its Treatment on Parathyroid Circadian Rhythmicity and Parathyroid Target-Organ Sensitivity J. Clin. Endocrinol. Metab., March 1, 2006; 91(3): 913 - 919. [Abstract] [Full Text] [PDF]

				S. Bonadonna, A. Burattin, M. Nuzzo, G. Bugari, E. A. Rosei, D. Valle, N. Iori, J. P Bilezikian, J. D Veldhuis, and A. Giustina Chronic glucocorticoid treatment alters spontaneous pulsatile parathyroid hormone secretory dynamics in human subjects Eur. J. Endocrinol., February 1, 2005; 152(2): 199 - 205. [Abstract] [Full Text] [PDF]

				A. D. Conigrave, H.-C. Mun, L. Delbridge, S. J. Quinn, M. Wilkinson, and E. M. Brown L-Amino Acids Regulate Parathyroid Hormone Secretion J. Biol. Chem., September 10, 2004; 279(37): 38151 - 38159. [Abstract] [Full Text] [PDF]

				S. Yamada, S. Saeki, I. Takahashi, K. Igarashi, H. Shinoda, and H. Mitani Diurnal Variation in the Response of the Mandible to Orthopedic Force J. Dent. Res., October 1, 2002; 81(10): 711 - 715. [Abstract] [Full Text] [PDF]

				D. J. Sherrard Manipulating the Calcium Receptor J. Am. Soc. Nephrol., April 1, 2002; 13(4): 1124 - 1125. [Full Text] [PDF]

				M. U. Karkkainen, C. J. Lamberg-Allardt, S. Ahonen, and M. Valimaki Does it make a difference how and when you take your calcium? The acute effects of calcium on calcium and bone metabolism Am. J. Clinical Nutrition, September 1, 2001; 74(3): 335 - 342. [Abstract] [Full Text]

				T. A Ricci, S. B Heymsfield, R. N Pierson Jr, T. Stahl, H. A Chowdhury, and S. A Shapses Moderate energy restriction increases bone resorption in obese postmenopausal women Am. J. Clinical Nutrition, February 1, 2001; 73(2): 347 - 352. [Abstract] [Full Text] [PDF]

				C. E. Hotchkiss and C. P. Jerome Evaluation of a nonhuman primate model to study circadian rhythms of calcium metabolism Am J Physiol Regulatory Integrative Comp Physiol, August 1, 1998; 275(2): R494 - R501. [Abstract] [Full Text] [PDF]

				G. E.-H. Fuleihan, E. B. Klerman, E. N. Brown, Y. Choe, E. M. Brown, and C. A. Czeisler The Parathyroid Hormone Circadian Rhythm Is Truly Endogenous--A General Clinical Research Center Study J. Clin. Endocrinol. Metab., January 1, 1997; 82(1): 281 - 286. [Abstract] [Full Text] [PDF]