鋅缺乏與生長遲滯

Zinc Deficiency and Failure to Thrive

兒童生長遲滯常會影響免疫功能導致反覆感染、身材矮小、與精神運動發展遲緩，此情況在已開發國家並不少見。大多數生長遲滯的原因是攝食量不足或是營養不均衡，例如鋅缺乏。鋅是一種參與許多細胞生化代謝的多功能微量元素，鋅在核酸代謝、細胞複製、組織修復與再生扮演重要角色，它同時具有抗氧化及抗發炎之特質。鋅缺乏出現於遺傳疾病如腸病性肢端皮炎，及後天因素如營養不均衡或不足、腸吸收疾病、鋅流失過多等。鋅缺乏時會表現生長遲滯、皮炎、禿髮、性腺功能受損、容易感染、傷口癒合延遲、對生長激素缺乏症治療作用不佳等。鋅離子主要存在細胞內，因此不容易由血中濃度直接判讀，目前採用血清鋅/ 銅比例為評估鋅缺乏較可行之指標。已有許多研究顯示補充鋅製劑對於兒童生長發育的正面效果，尤其是有鋅缺乏的營養性生長遲滯情況，一般建議治療使用較高劑量並至少六個月以上會有更佳效果。

Failure to thrive (FTT) is one of the most important causes leading to compromised immunity against infection, impairments of growth and weight gain, and psychomotor retardation among young children. FTT is surprisingly not uncommon in developed countries. Most cases of FTT are resulted from inadequate food or unbalanced nutritional intake, such as zinc deficiency. Zinc, as a multipurpose trace element, is involved in numerous aspects of cellular metabolism. Zinc also plays important roles in nucleic acid metabolism, cell replication, tissue repair and growth, as well as antioxidant and anti-inflammatory properties. Low zinc levels could be seen in inherited disorder such as acrodermatitis enteropathica, or acquired conditions including inadequate nutritional intake, malabsorption, excessive loss of zinc, or a combination of these factors. Zinc deficiency may be associated with growth retardation, dermatitis, alopecia, compromised gonadal function, susceptibility to infections, delayed wound healing, and even growth hormone (GH) resistance during the treatment of GH deficient children. Zinc is primarily an intracellular ion and is not as readily detectable as iron. However, measurement of the serum zinc/copper ratio is still considered to be the most reliable means of diagnosing zinc deficiency. Many researches have proven the effect of zinc on growth and development in terms of anthropometric measurements and biochemical parameters. When facing a child with nutritional FTT, it is reasonable to provide zinc replacement both for those with zinc deficiency, and this approach may take longer period of time(e.g., at least 6 months) with higher doses to be proven more efficacious.