钙可预防甲状旁腺功能亢进

一项基于护士健康研究的数据分析显示，女性钙摄入量增加与原发性甲状旁腺功能亢进风险降低有关(BMJ 2012;345:e6390)。

在这项据称是首次前瞻性评估甲状旁腺功能亢进与钙摄入量之间关联的研究中，布里格姆妇女医院的Julie M. Paik博士及其同事对护士健康研究Ⅰ中的58,354名女性进行了分析。护士健康研究Ⅰ是从1976年开始的一项前瞻性队列研究，受试者均每2年填写1次调查问卷。研究者采用饮食频次量表了解受试者的膳食摄入情况，涵盖130多种食物和22种软饮料。并且询问了钙、维生素D补充剂及多维元素的使用情况，根据品牌、种类和使用频次估算钙摄入量。

本项研究仅纳入在1986年交回量表至2008年5月之间被诊断为原发性甲状旁腺功能亢进的患者，结果共入组277例患者。在根据年龄对数据进行校正之后，研究者发现，与膳食钙摄入量处于最低五分位者相比，最高五分位的女性罹患甲状旁腺功能亢进的相对风险(RR)为0.61[95%置信区间(CI)，0.42~0.90；P=0.03]。

进一步校正体重指数、种族、吸烟、钙补充剂使用、维生素D摄入、膳食维生素A和蛋白质摄入、饮酒以及利尿剂使用等因素之后，膳食钙摄入量与甲状旁腺功能亢进风险之间的关联更加紧密：摄入量处于最高五分位的女性的RR值为0.56(95%CI，0.37~0.86；P=0.009)。

“尽管使用具体某种钙补充剂的原发性甲状旁腺功能亢进病例数过少”，但研究者还是对钙补充剂摄入量的影响进行了分析，并且从1994年坚持随访至2008年。结果显示，在985,628人-年的随访中，共发生257例偶发原发性甲状旁腺功能亢进。在校正年龄之后，“与不服用钙补充剂者相比，服用钙补充剂超过500 mg/d的女性罹患原发性甲状旁腺功能亢进的RR值为0.69(95%CI，0.50~0.94；P＜0.001)”。

与膳食钙摄入量一样，在多变量分析中(包括校正膳食钙摄入量)，钙补充剂摄入量与原发性甲状旁腺功能亢进风险的关联愈发强烈：高摄入量组相对于不摄入组的RR值为0.41(95%CI，0.29~0.60；P＜0.001)。

研究者也承认，上述分析结果未必能外推至男性和非白人女性。另外，“尽管饮食频次量表设计很严谨，但本项研究对钙摄入量的评估还算不上完美”。“不过，由于采用了前瞻性设计，对病例状态的任何误分类都是随机的，因此可能会低估钙摄入量与原发性甲状旁腺功能亢进风险之间负相关的程度。”

研究者报告称无相关利益冲突。这项研究获得了国立卫生研究院的基金资助。

随刊述评：补钙利大于弊

坦帕市总医院诺曼甲状旁腺中心外科主任James Norman博士在随刊述评中指出：“鉴于钙对于骨骼健康的益处，数十年来，多数临床医生都会建议患者摄入适量的钙。”然而，近年来，这一建议受到了一些质疑，“越来越多的证据提示，服用钙补充剂可能与心肌梗死风险增加有关”。以致于一些有明显骨质疏松的患者也会对是否服用钙补充剂感到犹豫(BMJ 2012;345:e6646)。

在本项研究中，Paik及其同事发现即使钙摄入量低达500 mg/d仍可降低原发性甲状旁腺功能亢进风险。这一发现非常重要，因为如此低的摄入量不会有太多争议。他还表示，这项研究结果“可以使临床医生更有信心地鼓励女性患者服用钙补充剂”。

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By: DENISE NAPOLI, Cardiology News Digital Network

Increased calcium intake is associated with a reduced risk for primary hyperparathyroidism in women, according to an analysis of data from the Nurses’ Health Study published on Oct. 18.

In what the researchers called the first prospective study to assess the link between hyperparathyroidism and calcium intake, Dr. Julie M. Paik of Brigham and Women’s Hospital in Boston and her colleagues looked at 58,354 women from the Nurses’ Health Study I, an ongoing, prospective cohort study that began in 1976. Participants in the study complete questionnaires every 2 years.

Dietary intake was assessed using the food frequency questionnaire, which asked about participants’ average intake of more than 130 individual food items and 22 beverages during the previous year.

The survey also asked about calcium supplements, vitamin D supplements, and multivitamins, with calcium intake determined by the brand, type, and frequency of use.

Only cases of primary hyperparathyroidism diagnosed between the date on which the 1986 questionnaire was returned and May 31, 2008, were included in the study.

Overall, during 1,475,978 person-years of follow-up, there were 277 cases of incident primary hyperparathyroidism.

After the data were adjusted for age, women in the highest quintile of dietary intake had a relative risk for developing hyperparathyroidism of 0.61, compared with women in the lowest quintile (95% confidence interval, 0.42-0.90; P = .03), the investigators reported (BMJ 2012;345:e6390).

Further adjustments for body mass index, race, smoking, calcium supplement use, intake of vitamin D, dietary intake of vitamin A and protein, alcohol intake, and diuretic use only strengthened the effect: The relative risk among the highest quintile of intake was 0.56, by this calculation, compared with patients in the lowest intake category (95% CI, 0.37-0.86; P = .009).

The authors also looked at supplemental calcium intake, although "because of an insufficient number of cases of primary hyperparathyroidism among the different categories of supplemental calcium use in the earlier time periods, our analysis on the relation between supplemental calcium intake and primary hyperparathyroidism began in 1994 with follow-up until 2008," wrote Dr. Paik and her coinvestigators.

In this analysis, which included 985,628 person-years of follow-up, there were a total of 257 cases of incident primary hyperparathyroidism.

When the findings were adjusted for age, "the relative risk for women taking more than 500 mg/day of calcium supplements compared with those not taking calcium supplements was 0.69 (95% CI, 0.50-0.94; P less than .001)," wrote the authors.

As with dietary intake, the protective effect was only strengthened in multivariable analysis, including adjustment for dietary calcium: The higher-intake group’s risk was 0.41, compared with the lower-intake group (95% CI, 0.29-0.60; P less than .001).

The authors conceded that the study population was exclusively female and almost entirely white, making the findings not necessarily generalizable to men or to women of other races.