Iodine nutrition of pregnant and lactating women in Hong Kong, where intake is of borderline sufficiency

OBJECTIVE: To describe the iodine nutrition of pregnant and lactating women in Hong Kong, where intake is of borderline sufficiency.DESIGN: Review of cross-sectional and prospective studies.SETTING: China, Hong Kong Special Administrative Region (SAR).SUBJECTS: Pregnant and lactating women.RESULTS: Studies of pregnant women in Hong Kong SAR have revealed an increase in the urinary iodine (UI) concentration as pregnancy advances. A significant percentage of women had a sub-normal serum thyroid hormone concentration at full term. Although iodine is concentrated by the mammary gland, 19% of all mothers had low iodine concentrations in their breast milk. The moderate correlation between the concentrations of iodine in breast milk and urine suggests that an adequate maternal urinary iodine concentration cannot reliably indicate that an infant is getting enough iodine in breast milk. Therefore, some breast-fed infants may still be at risk of low iodine intake, and additional iodine supplements, other than salt iodisation, would be warranted in this population.CONCLUSIONS: The currently recommended intake of iodine through universal salt iodisation may not be adequate for pregnant and lactating women, and supplementation during pregnancy and lactation should be further considered in light of the latest recommendations.published_or_final_versio

The effect of thyroid hormone on bone metabolism and osteoporosis

Thyrotoxicosis has long been known to accelerate bone turnover and thus increase the risk for developing osteoporosis, especially in peri- and postmenopausal women. Increasingly sophisticated tests of thyroid function have indicated that minor degrees of hyperthyroidism are common in patients taking thyroxine (T4) therapy. Recent reports have suggested that women taking TSH-suppressive doses of T4 have reduced bone density. An overview of the effects of thyroid hormone on bone metabolism is presented. The use of sensitive TSH assays can now permit extremely accurate titration of the T4 dosage and should obviate the potential side effects of excessive therapy that results in iatrogenic subclinical thyrotoxicosis.published_or_final_versio

Japanese seaweed and thyroid problems

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A rat model of thyroid hormone-induced bone loss: Effect of antiresorptive agents on regional bone density and osteocalcin gene expression

Thyroid hormone has been shown to stimulate bone resorption. Both endogenous hyperthyroidism and exogenous thyroxine suppressive therapy have been associated with reduction in bone mineral density (BMD), but the patholophysiology of thyroxine-induced bone loss is not well understood. First we studied the effect of L-T4 (0.1-0.3 μg/g body weight ip/day) on bone turnover in rats by measuring regional BMDs and osteocalcin mRNA. Next we determined whether antiresorptive agents (calcitonin 1 μU/g ip/day or sodium etidronate given cyclically at 10 μg/g po for 3 consecutive days out of every week) could prevent bone loss. Groups of 10 male Sprague-Dawley rats each weighing 320-350 g were studied before and after 3 weeks of treatment. L-T4 treatment resulted in reduction in BMDs in the lumbar spine, tail, and femur as measured by dual energy X-ray absorptiometry, but there was no correlation with the dosage of L-T4 or the serum T4 level. Treatment with sodium etidronate or calcitonin alone did not alter the regional BMD. Cyclical sodium etidronate, but not calcitonin, was able to prevent the bone loss induced by L-T4 treatment. L-T4 caused a dose-dependent increase in femur osteocalcin mRNA concentration. Treatment with calcitonin resulted in 50% reduction of osteocalcin mRNA, but sodium etidronate had no effect. In conclusion, cyclical sodium etidronate prevents bone loss induced by exogenous L-T4 in rats and may be useful in preventing osteoporosis in patients given long term TSH-suppressive doses of thyroxine therapy.published_or_final_versio

Knowledge of vitamin D and perceptions and attitudes toward sunlight among Chinese middle-aged and elderly women: A population survey in Hong Kong

Background: Physical and biological risk factors for vitamin D inadequacy are known; however, cultural- and population-specific behaviours and attitudes that influence these risk factors, particularly among Asian people, are less well documented. To understand more about prevailing attitudes and behaviour toward sunlight and knowledge of vitamin D among a population at greater risk of impaired vitamin D status, poor bone health and osteoporosis, we conducted a telephone interview survey of 547 middle-aged and elderly Chinese women living in Hong Kong. Methods: All telephone interviews were conducted using the Computer Assisted Telephone Technique and target respondents were selected by random sampling. Interviews were conducted in Cantonese and eighteen main questions were asked pertaining to personal characteristics, perceptions, attitudes and behaviour toward sunlight, and knowledge about vitamin D. Results: The survey results showed that 62.3% (n = 341) did not like going in the sun and 66.7% of respondents spent an average of 6-10 hours indoors, between 6:30 am and 7:00 pm, during weekdays. However, 58% of people thought that they had enough exposure to sunlight. The majority had heard of vitamin D, but knowledge about the role and sources of vitamin D was low. Among those who knew that sunlight was a source of vitamin D, the majority spent less than 1 h in the sun in the past week (76.4% vs 23.6%, 1 h in the sun in the past week, chi-square p < 0.05). There were significantly more users of sunscreen products (75.5% vs 53.0%, p < 0.0001, sunscreen users vs non-users) and parasols (68.4% vs 43.7%, p < 0.0001, parasol users vs non-users) among respondents who knew that vitamin D was good for bone health and that sunlight was a source of vitamin D. Age, occupation, subjects who liked going in the sun were factors associated with awareness of vitamin D but age was the only predictive factor for giving correct answers to the actions and sources of vitamin D. Conclusion: The survey revealed considerable ignorance and confusion about the role of sunlight in vitamin D production, and the function and sources of vitamin D. Attitudes and behaviour toward sunlight were largely negative and many took measures to avoid sunlight, particularly among younger (middle-aged) women who had good awareness of vitamin D. © 2006 Kung and Lee; licensee BioMed Central Ltd.published_or_final_versio

Predictors of low bone mass in young Chinese women

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Development of murine model of autoimmune thyroiditis induced with homologous mouse thyroid perioxidase

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Gamma-interferon activates a nuclear protein that binds to the gamma-interferon activation site of the thyroglobulin gene

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Characterization of thyroid-stimulating blocking antibodies that appeared during transient hypothyroidism after radioactive iodine therapy

Hypothyroidism after radioactive iodine (RAI) therapy for Graves' disease can be transient or permanent. The cause for early transient hypothyroidism is unknown. We evaluated 11 patients who developed transient hypothyroidism within 6 months of RAI and 12 who remained euthyroid after RAI. Approximately equal numbers of patients in each group had thyroid-stimulating antibody (TSAb) that increased cyclic adenosine monophosphate (cAMP) levels in Chinese hamster ovary (CHO) cells transfected with the recombinant human thyrotropin receptor (TSHR) (WT cells). Approximately equal numbers of patients from both groups had an increase in TSAb activity post-RAI. All TSAbs had their dominant functional epitope on the N-terminus of the TSHR extracellular domain, requiring residues 90-165 for activity because they, but not TSH, completely lost stimulating activity in a receptor chimera, wherein TSHR residues 90-165 were substituted by equivalent residues of the lutropin/choriogonadotropin receptor (LH/CGR). Although equal numbers of patients in both groups had thyrotropin-binding inhibiting immunoglobulin activity (TBII), as measured by radioreceptor assay before RAI, patients with transient hypothyroidism had a surge in TBII activity and all except one became positive for thyroid-stimulating blocking antibodies (TSBAb), as measured by inhibition of TSH-stimulated cAMP from WT cells. When immunoglobulin G (IgGs) were epitope-mapped using TSHR/LH-CGR chimeras with different substitutions, 8 hypothyroid subjects had TSBAbs directed against residues 90-165 of the TSHR, as well as TSHR residues 261-370. Two had functional epitopes directed at residues 9-89 as well as TSHR residues 261-370. None of the euthyroid control patients developed TSBAbs and their TBII activity decreased post-RAI. When patients with transient hypothyroidism reverted to a euthyroid state, TSAb was still detectable in 5; however, TBII was present in all and TSBAb, although decreased, was still positive in 9. In summary, RAI therapy was associated with a change in thyroid antibody characteristics in most patients. Additionally, patients with a surge in TBII and the appearance of TSBAb developed transient hypothyroidism after RAI.published_or_final_versio

Changes in cytokine production during pregnancy in patients with Graves' disease

In order to investigate the role of type 1 and type 2 cytokines in the remission of Graves' disease (GD) during pregnancy, spontaneous and mitogen-stimulated production of interleukin (IL)-4, IL-6, IL-10, IL-12, interferon-γ (IFN-γ), and tumour necrosis factor-α (TNF-α) were measured by enzyme-linked immunospot assay of peripheral blood mononuclear cells from 10 pregnant women with GD, 8 healthy pregnant women, and 10 healthy nonpregnant women. Tests were performed in the first, second, and third trimesters of pregnancy and 10-17 weeks after delivery. IL-4 production was not affected greatly by normal or GD pregnancy, whereas IFN-γ production was suppressed throughout pregnancy but returned to normal levels after delivery in both controls and patients. IL-6 and TNF-α tended to be higher in GD pregnancy than normal pregnancy, especially in the second and third trimesters. Controls had raised IL-10 in the first trimester with a return to normal levels by the third trimester, whereas patients had raised levels throughout pregnancy. IL-12 levels were suppressed to a greater extent in control than Graves' pregnancy, especially during the second and third trimesters. Ratios of IL10:IL12 in phytohemaglutinin (PHA)-stimulated cultures were much lower in GD than normal pregnancy and cross-regulation of IL-10 and IL-12 may be deficient in GD.published_or_final_versio