Combined Impairment of Nutritional Parameters and Thyroid Homeostasis in Mildly Iodine-Deficient Children

Abstract

The relation between thyroid homeostasis and the biochemical parameters of subclinical protein malnutrition has been analyzed in schoolchildren in a rural area in the south of Italy, known to be moderately iodine-deficient. The sera of 32 children (15 males and 17 females aged 6 to 11 years) have been analyzed. These children were divided into two groups, according to thyroid function: (1) 16 euthyroid children (mean thyrotropin [TSH] 2.38 +/- .35 mU/L; 6 with goiter) and (2) 16 subclinical hypothyroid children (mean TSH 7.32 +/- 1.68 mU/L; 6 with goiter). Retinol circulating complex (RCC) components were determined in serum by high-performance liquid chromatography (HPLC) and radial immunodiffusion and the essential and nonessential amino acid levels by ion exchange chromatography. Reduced retinol binding protein (RBP) and transthyretin (TTR) levels were recorded in the sera of 11 of 32 (34%) and in 5 of 32 (16%) patients, respectively. The linear regression analysis revealed that RBP and TSH levels were inversely correlated (r = -0.514; p < 0.0026). The RBP levels were subnormal in 2 of 16 euthyroid and in 9 of 16 hypothyroid patients (Fisher test p < 0.023), and the mean RBP levels were significantly reduced in the hypothyroid patients when compared with those of the euthyroid group (p < 0.0026). The retinol/RBP ratio was also significantly different between euthyroid and hypothyroid children (0.75 vs. 0.95; p < 0.0002). The mean essential amino acid levels, with the exception of methionine, were all in the normal range. The selected amino acid ratios confirmed that the patients were exposed to mild protein malnutrition. These results provide evidence that even mild protein-energy malnutrition may have detrimental effects on thyroid homeostasis in iodine-deficient areas.

Low Levels of Plasma Proteins: Malnutrition or Inflammation?

“…In addition to most of the factors listed in Table 1, the levels of these proteins are affected by levels of their physiologic ligands: iron in the case of transferrin and retinol (vitamin A) for RBP (34). In the presence of iodine deficiency with elevated thyroid stimulating hormone (TSH) levels, RBP levels are proportionately lower (35). Although transferrin levels fall markedly during starvation (21), studies in children with severe PEM have shown only fair correlation between plasma transferrin levels and clinical indices of wasting (36).…”

Interactions of Thyroid Hormones; Insulin-like Growth Factor-1 (IGF-1), IGF Binding Proteins, and Nutritional Anthropometric Parameters in School Children with Goiter Detected by Palpation

“…Similarly lower weight and height of children with goiter compared to their healthy peers in this study indicates the presence of nutritional insuffi ciency in children with palpable goiter. Centanni reported that even mild protein-energy malnutrition may have detrimental eff ects on thyroid homeostasis in iodine-deficient areas ( Centanni et al, 1998 ). Long lasting insuffi cient nutrition causes cessation of growth and results in nutritional growth retardation (NGR).…”

Interaction of two public health problems in Turkish schoolchildren: nutritional deficiencies and goitre

“…Moreover, PEM may contribute directly to goitrogenesis through the lack of substrate availability, particularly essential amino acids such as tyrosine 21 . Even mild PEM is reported to have detrimental effects on thyroid homeostasis in iodinedeficient areas 22 . Goitre detection rate was highest in children with low and especially very low socio-economic status.…”

“…A low weight-for-age Z-score (WAZ) (, -2SD) is considered to indicate underweight in the absence of significant wasting 10 -12 . In addition, BMI values less than 15 kg m 22 indicate total body fat content below 5% of body weight. That BMI is an important index of being thin was interpreted in children over 10 years of age 13 .…”