Is it possible that a combined oral contraceptive, Follimin, gives hypocalcemia and changes the wel

Fråga: Is it possible that a combined oral contraceptive, Follimin, gives hypocalcemia and changes the well regulated calcium balance? See letter.

Sammanfattning: Estrogen is well known to have a negative influence on bone resorption and thus will produce a hypocalcuric effect and conceivably could reduce serum calcium levels as well. Oral contraceptives containing estrogen may share these effects. It is unlikely that this estrogen effect could produce overt hypocalcemia, but since there is a link between estrogen and calcium homeostasis this case should be reported to the Drug Side Effects Committee.

Svar: Estrogens are known to have an effect on calcium homeostasis. When estrogens are administered to post-menopausal women, there is no decrease in the absorption of dietary calcium, while the amount of calcium excreted in the urine diminishes, resulting in an improved calcium balance. This hypocalcuric effect is considered to be secondary to diminished release of calcium from bone and increased skeletal calcium retention, rather than the result of a primary effect of estrogen upon calcium excretion by the kidney. Estrogens decrease the responsiveness of bone to the resorptive action of parathyroid hormone, diminish the rates of bone resorption and formation and arrest or retard bone loss in osteoporotic women (1,2).

Investigations examining the activity of oral contraceptives containing a relatively small amount of estrogens have shown that serum calcium levels fall (3) and urinary excretion of calcium decreases (2). It must be pointed out that in one of these studies, no effect on serum calcium was noted (2), while in the other (3) a statistically significant but clinically insignificant decrease was noted. Neither study indicated that clinical hypocalcemia was a potential side effect of oral contraceptive use. Furthermore, we have been unable to find any documented case reports to suggest this possibility. 1 Goodman and Gilman, The pharmacological basis of therapeutics, 1980; 6th ed: 1442-1447 2 Goulding A, McChesney R: Oestrogen-progestogen oral contraceptives and urinary calcium excretion. Clin Endocrinol 1977; 6: 449-454 3 Simpson GR, Dale E: Serum levels of phosphorus, magnesium, and calcium in women utilizing combination oral or long-acting injectable progestational contraceptives. Fertil Steril 1972; 23: 326-330