青少年减肥手术前应查维生素D

休斯敦——美国内分泌学会年会上公布的一项回顾性分析显示，在减肥手术前进行实验室检查的219例肥胖青少年患者中，54%存在维生素D缺乏(包括9%的严重缺乏者)。82%青少年血液中的25-羟基维生素D(25OHD)不足。

在这项研究中，纽约哥伦比亚大学的Marisa Censani博士及其同事从2006年3月~2011年6月在其医院接受减肥手术的所有青少年患者中，查找到219例具有血清25OHD和甲状旁腺激素水平记录。这些青少年均符合接受减肥手术的标准，即达到Tanner 4期或5期，并且体重指数(BMI)＞50 kg/m2，或如果具有合并症则BMI＞35 kg/m2。该队列65%为女性，43%为白人，35%为西班牙裔，15%为非裔美国人，其余为其他族裔。患者的平均年龄为16岁(13~18岁)，平均BMI为48 kg/m2。

该研究将血清250OHD水平≥30 ng/ml定义为充足，20~29 ng/ml为不足，＜20 ng/ml为缺乏，＜10 ng/ml为严重缺乏。这些青少年的平均血清25OHD水平为21 ng/ml，属于不足。仅18%患者的25OHD充足。29%为25OHD不足，45%为25OHD缺乏，9%为25OHD严重缺乏。

BMI最高者出现25OHD缺乏的可能性最大。BMI每增加1 kg与25OHD水平降低0.2 ng相关。维生素D缺乏最常见于非裔美国人，82%的非裔美国人缺乏维生素D，并且无1人的水平在正常范围内。59%的西班牙裔美国人和37%的白人缺乏维生素D。种族是25OHD水平的最显著预测因素。

在非裔美国人中，约80%缺乏维生素D，其余的维生素D水平不足。在西班牙裔美国人中，近60%缺乏维生素D，近25%的维生素D水平不足，约25%的维生素D水平充足。在白人中，各有近40%的维生素D水平缺乏或不足，20%以上的维生素D水平充足。

5%的患者出现明确的继发性甲状旁腺功能亢进，尽管血清甲状旁腺激素水平的变化与25OHD呈负相关。非裔美国人、BMI和甲状旁腺激素水平可解释患者间25OHD水平的差异。

Censani博士建议，所有的病态肥胖青少年均应筛查有无维生素D缺乏，并且缺乏维生素D者应接受相应治疗。不过，有与会者指出，目前尚无证据表明这一做法具有临床益处。Censani博士对此表示认同，并称未来还需开展更多研究。

该研究的优点在于样本量大且所研究的种族相对较多，局限性在于缺乏基于社区的非肥胖对照组及缺乏有关膳食钙和维生素D摄入、日晒或骨密度的数据。

该研究获美国国立卫生研究院资助。Censani博士声明无经济利益冲突。

爱思唯尔  版权所有

By: SHERRY BOSCHERT, Clinical Endocrinology News Digital Network

HOUSTON – Fifty-four percent of 219 obese adolescents being evaluated for bariatric surgery were deficient in vitamin D, including 9% who were severely deficient, a retrospective analysis of preoperative laboratory measures found.

Eighty-two percent of the adolescents had insufficient levels of 25-hydroxyvitamin D (25OHD) in their blood, Dr. Marisa Censani and her associates reported at the annual meeting of the Endocrine Society.

The findings are so striking that all morbidly obese adolescents should be screened for vitamin D deficiency, and those who are deficient should be treated to replete vitamin D levels, suggested Dr. Censani of Columbia University, New York.

It’s particularly important to screen adolescents before bariatric surgery procedures, some of which have been associated with bone loss, which results from weight loss and decreased calcium and vitamin D absorption. Preoperative vitamin D deficiency could put adolescent patients at greater risk because they have not reached their peak bone mass, she said.

Previous studies have shown that obese adults undergoing bariatric surgery commonly are vitamin D deficient before surgery, but these are some of the first data in preoperative adolescent patients.

Of all adolescents undergoing bariatric surgery at her institution from March 2006 to June 2011, 219 had records on serum 25OHD and parathyroid hormone levels. The cohort was 65% female, 43% white, 35% Hispanic, and 15% African American, with the rest being other races/ethnicities. Patients had a mean age of 16 years (ranging from 13-18 years) and a mean body mass index of 48 kg/m2.

The mean serum 25OHD level was 21 ng/mL, which was considered insufficient. The study defined adequate levels of serum 25OHD as at least 30 ng/mL, insufficient levels as 20-29 ng/mL, deficient levels as less than 20 ng/mL, and severely deficient levels as less than 10 ng/mL.

Only 18% of patients had sufficient 25OHD levels. Twenty-nine percent had insufficient levels, 45% were vitamin D deficient, and 9% were severely deficient.

Patients with the highest BMIs were most likely to have deficient levels of 25OHD. Every kilogram increase in BMI correlated with a 0.2-ng decrease in 25OHD levels, Dr. Censani said.

Vitamin D deficiency was most common in African Americans, 82% of whom were deficient and none of whom had levels in the normal range. Fifty-nine percent of Hispanics and 37% of whites had vitamin D deficiency. Race was the strongest predictor of 25OHD levels.

Roughly 80% of African American patients were deficient in vitamin D and the rest had insufficient levels. In Hispanics, nearly 60% were deficient in vitamin D, close to 25% had insufficient levels, and about 25% had adequate levels. In whites, deficient or insufficient levels each were seen in nearly 40% of patients, with adequate levels in more than 20%.

Clear secondary hyperparathyroidism was seen in 5% of patients, though serum parathyroid levels varied inversely with 25OHD. African American race, BMI, and parathyroid levels explained 21% of the variance in 25OHD levels between patients.

To be eligible for bariatric surgery, adolescents had to have reached Tanner stage IV or V and had to have a BMI greater than 50, or above 35 kg/m2 if they had comorbidities.

A physician in the audience challenged Dr. Censani’s recommendation that all obese adolescents be screened and possibly treated for vitamin D deficiency, saying there is no evidence yet of clinical benefit from that approach. Dr. Censani agreed that more research is needed to support this strategy.

The current study was limited by the lack of a community-based, nonobese control group and lack of data on dietary calcium and vitamin D intake, sun exposure, or bone mineral density. The study’s large size and relatively good ethnic diversity are strengths, she said.

The U.S. adolescent obesity rate has more than tripled in the past 30 years, with 16% of children and adolescents now overweight, 4% obese, and 4% morbidly obese, studies suggest.

Dr. Censani reported having no financial disclosures. The National Institutes of Health funded the study.