This Article Full Text (PDF) Submit a related Letter to the Editor Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Copyright Permission Citing Articles Citing Articles via Google Scholar Google Scholar Articles by VILLA, M. L. Articles by MARCUS, R. Search for Related Content PubMed PubMed Citation Articles by VILLA, M. L. Articles by MARCUS, R.

Effects of Aluminum Hydroxide on the Parathyroid-Vitamin D Axis of Postmenopausal Women^*

MARIE LUZ VILLA, ELIZABETH PACKER, MANDEEP CHEEMA, LEAH HOLLOWAY and ROBERT MARCUS

Aging Study Unit, Geriatrics Research, Education and Clinical Center, VA Medical Center Palo Alto; Palo Alto, California 94304 Department of Medicine, Stanford University Stanford, California 94300

Address requests for reprints to: Robert Marcus, M.D., Grecc 182-B, VA Medical Center, 3801 Mirande Avenue, Palo Alto, California 94304.

In previous studies we proposed that estrogen increases circulating calcitriol in postmenopausal women by reducing plasma phosphorus concentrations. For this model to be plausible, a reduction in plasma phosphorus must by itself be sufficient to increase circulating calcitriol in elderly women. To assess this question we studied the effects of A1(OH)³ on daylong circulating levels of phosphorus, calcium, PTH, and calcitriol in 14 postmenopausal women. Subjects were studied on two 7-day periods of dietary control, in which calculated intakes for phosphorus, calcium, and sodium were 950, 800, and 3000 mg/day, respectively. During one randomly assigned period, subjects were given A1(OH)³ with each meal. A1(OH)³ significantly lowered daylong plasma phosphorus concentrations by 17% (0.95 ± 0.02 mmol/L vs. 1.15 ± 0.02, P < 0.0005) (2.94 ± 0.06 mg/dL vs. 3.57 ± 0.07), and this was associated with a 38% rise in circulating calcitriol from 61.8 ± 10.3 pmol/L to 85.2 ± 10.1 pmol/L (25.7 ± 4.3 pg/ml to 35.5 ± 4.2 pg/ml) (P < 0.0001). The rise in calcitriol correlated significantly with the reduction in phosphorus (r = 0.51, P = 0.03). A1(OH)³ did not significantly alter average daily circulating total calcium (2.32 ± 0.008 vs. 2.32 ± 0.005 mmol/L) (9.31 ± 0.03 us. 9.29 ± 0.02 mg/dL), ionized calcium (1.19 ± 0.003 vs. 1.19 ± .004 mmol/L), or intact PTH (24.6 ± 0.6 vs. 24.2 ± 0.8 ng/L). Moreover, neither the renal phosphorus reabsorption maximum (TmP/GFR), baseline excretion of cAMP, nor the phosphaturic, cAMP, or calcitriol responses to infused hPTH(l–34) were altered by A1(OH)³. We conclude that A1(OH)³ treatment of older women lowers plasma phosphorus concentrations by restricting intestinal phosphorus absorption, and that older women retain the capacity to increase calcitriol levels in response to phosphorus restriction.

^* This project was supported by the Research Service of the Department of Veterans Affairs.

Recipient of a VA Geriatrics Fellowship.

Received March 5, 1991.