老年人血管性痴呆与甲状腺轴功能关系的研究

目的　探讨老年人血管性痴呆（VD）与甲状腺轴功能的关系。　方法　采用放射免疫分析法检测31例VD患者、22例不伴有痴呆的脑血管病（CVD）患者及22例同龄对照的血清三碘甲状腺原氨酸（T     

Thyroid hormones, dementia, and atrophy of the medial temporal lobe

CONTEXT: Thyroid function has been related to Alzheimer disease (AD), but it remains unclear whether thyroid dysfunction results from or contributes to developing AD. OBJECTIVE: The objective of the study was to determine the association between thyroid function and both medial temporal lobe atrophy on brain magnetic resonance imaging (MRI) as putative early sign of AD and risk of dementia. DESIGN AND PARTICIPANTS: This was a population-based cohort study among 1077 elderly subjects aged 60-90 yr and dementia free at baseline (1995-1996). MAIN OUTCOME MEASURES: Nonfasting serum levels of TSH, free T(4) (fT(4)), T(3), and rT(3) were available in 1025 subjects followed up for incident dementia until 2005. In a subset of 489 nondemented elderly, we assessed volumes of the hippocampus and amygdala on brain MRI. Subjects using thyroid medication were excluded. RESULTS: During 5657 person-years of follow-up (mean 5.5 yr), 63 subjects were diagnosed with dementia (46 with AD). TSH and thyroid hormones were not associated with risk of dementia or AD. TSH and T(3) were also not related to brain atrophy, whereas nondemented subjects with higher fT(4) levels had more hippocampal and amygdalar atrophy on MRI. Similar associations were found for rT(3). Excluding subjects with thyroid disorders or incipient AD did not change the results. CONCLUSION: In our study, TSH was related neither to risk of AD nor with early MRI markers thereof, arguing against an important role of thyroid function in the development of AD. Whether the association of higher fT(4) and rT(3) levels with brain atrophy on MRI has functional significance remains to be elucidated.     

THYROID HORMONES AND THE REGULATION OF THYROID FUNCTION IN MEN WITH COELIAC DISEASE

A specific pattern of thyroid hormone abnormalities was observed in twenty-seven men with coeliac disease which differed from that observed in patients with non-thyroidal illness (NTI). Serum free thyroxine (FT4) was reduced, but increased after gluten was withdrawn from the diet and jejunal morphology improved. Total T4 (TT4), total triodothyronine (TT3), free triiodothyronine (FT3) and reverse T3 (rT3) levels were unchanged, unlike the findings in nineteen men with Crohn's disease when TT3 fell, rT3 tended to rise but TT4, FT4 and FT3 levels were normal, except FT4 was significantly higher in a subgroup of patients who were more severely ill. The thyroid hormone changes in Crohn's disease are those expected in NTI. Basal serum thyrotrophin (TSH) was normal in all but one of the patients with coeliac disease but 45% of untreated coeliacs had exaggerated responses of TSH to thyrotrophin releasing hormone, an observation which cannot be explained as a feature of NTI. These changes in thyroid hormones in coeliac disease could not be attributed to abnormalities of thyroxine-binding globulin or thyroxine-binding prealbumin, and thyroid autoantibodies were not detected in these patients. Hence, different patterns of thyroid hormone abnormalities can occur in different diseases of the same organ in patients of equivalent nutritional status. Circulating gluten peptides may be involved in the hypothalamic-pituitary disturbance of coeliac disease.     

Change in serum thyroid hormone levels in patients with acute myocardial infarction

It has been reported that there is a decrease in the serum concentration of thyroid hormones in non-thyroidal illness. In the present study we made serial measurements of serum concentration of thyroid hormones [triiodothyronine (T3), thyroxine (T4), free triiodothyronine (FT3), free thyroxine (FT4), reverse triiodothyronine (rT3)], thyroid stimulating hormone (TSH) and thyroxine binding globulin (TBG) in 10 patients with acute myocardial infarction (AMI, Grade I, according to the classification of Killip & Forrester) during 14 days after onset. In the early phase of AMI, serum T3, T4, FT3 and FT4 levels decreased while rT3 increased. TSH and TBG levels, however, were unchanged. In the patients with a high peak creatine phosphokinase activity (greater than or equal to 400 mU/ml), the decrease in thyroid hormone and increase in serum rT3 levels were greater than in patients with a low peak value (less than 400 mU/ml), suggesting a correlation between severity of AMI and changes in serum thyroid hormone levels. Especially, serum FT3 levels fell below the lower limit of controls within 14 days, with the lowest levels and the rT3 peak on the third day after onset. These data suggest that in AMI peripheral conversion of T4 favours rT3 production and that low levels of serum FT3 and T3 protect the infarcted heart muscle against thyroid hormone action.     

The association of polymorphisms in the type 1 and 2 deiodinase genes with circulating thyroid hormone parameters and atrophy of the medial temporal lobe

CONTEXT: Thyroid function has been related to Alzheimer disease (AD) and neuroimaging markers thereof. Whether thyroid dysfunction contributes to or results from developing AD remains unclear. Variations in the deiodinase type 1 (DIO1) and type 2 (DIO2) genes that potentially alter thyroid hormone bioactivity may help in elucidating the role of thyroid function in AD. OBJECTIVE: We investigated the association of recently identified polymorphisms in the DIO1 (D1a-C/T, D1b-A/G) and DIO2 (D2-ORFa-Gly3Asp, D2-Thr92Ala) genes with circulating thyroid parameters and early neuroimaging markers of AD. DESIGN AND PARTICIPANTS: The Rotterdam Scan Study is a population-based cohort study among 1,077 elderly individuals aged 60-90 yr. MAIN OUTCOME MEASURES: DIO1 and DIO2 polymorphisms and serum TSH, free T4, T3, and reverse T3 (rT3) levels were determined in 995 nondemented elderly, including 473 persons with assessments of hippocampal and amygdalar volume on brain magnetic resonance imaging. RESULTS: Carriers of the D1a-T allele had higher serum free T4 and rT3, lower T3, and lower T3/rT3. The D1b-G allele was associated with higher serum T3 and T3/rT3. The DIO2 variants were not associated with serum thyroid parameters. No associations were found with hippocampal or amygdalar volume. CONCLUSION: This is the first study to report an association of D1a-C/T and D1b-A/G polymorphisms with iodothyronine levels in the elderly. Polymorphisms in the DIO1 and DIO2 genes are not associated with early magnetic resonance imaging markers of AD. This suggests that the previously reported association between iodothyronine levels and brain atrophy reflects comorbidity or nonthyroidal illness rather than thyroid hormones being involved in developing AD.     

老年非甲状腺疾病患者甲状腺功能检测及评价

本文对老年非甲状腺疾病患者107例、健康老年人30例的血清T_3、T_4、FT_3、FT_4、γT_3、TSH水平进行测定。结果表明,老年心血管疾病、恶性肿瘤、肺部疾病、糖尿病、肝病患者T_3明显降低(P<0.05),FT_3显著降低(P<0.01),γT_3显著增高(P<0.01)。老年其他疾病(神经系疾病、胆囊炎等)T_3虽无明显变化,但FT_3仍明显降低(P<0.05)。T_4仅在肺部疾病患者明显降低(P<0.05),其余各组T_4、FT_4、TSH均无显著改变,健康老年T_3较健康成年人明显降低(P<0.05),其变化程度与疾病严重程度有一定关系,其中以FT_3更为敏感。故认为,测定甲状腺激素水平对判断老年患者病情、估计预后有重要参考价值。     

Thyroid function, morphology and prevalence of thyroid disease in a population-based study of Danish centenarians.

OBJECTIVES: To investigate thyroid function, morphology, and autoimmunity in relation to physical function in an unselected population of centenarians. DESIGN: A population-based survey. SETTING: Denmark. PARTICIPANTS: All persons living in Denmark who celebrated their 100th anniversary during the period April 1, 1995 to May 31, 1996, a total of 276 persons. MAIN OUTCOME MEASUREMENTS: Thyroid hormones (TSH, T4, FT4I, T3, FT3I, and T3RU), thyroid autoantibodies (TPOab and Tgab), thyroid volume, activities of daily living according to the Katz Index of ADL. RESULTS: In all, 207 (75%) of the 276 eligible subjects participated, and 148 agreed to blood tests. Among the participants, 2.9% had previously known hyperthyroidism, and the same proportion had previously known hypothyroidism. The blood tests did not reveal any undiagnosed cases of overt thyroid dysfunction. However 7.2% had a subnormal serum TSH, and 2.9% had an elevated serum TSH; all had normal serum T3 and serum T4 levels. Thyroid autoantibodies were detected in 26 (17.6%) centenarians (11.5% had Tgab and 9.5% had TPOab). Among relatively independent centenarians, low serum T3 was significantly associated with high comorbidity (P = .029), whereas both low serum T3 and thyroid autoantibodies were significantly associated with ADL-dependency (P < .001 and P = .030, respectively). Ultrasonography (n = 50) revealed a small gland with a median volume of 8.3 mL (range 3.2-27.9) compared with an expected volume of 20 mL (14-26) (P < .001). There was no significant relationship to body weight. When examined by ultrasound, only 26% had significant morphological alterations. CONCLUSIONS: Thyroid dysfunction does not seem to be more prevalent among centenarians than among younger old people. Low serum T3 is related to poor physical function and co-morbidity, whereas thyroid autoimmunity is related only to poor physical functioning. Despite atrophy of the thyroid gland, these findings suggest that thyroid function is well preserved in centenarians.     

健康高龄老年人甲状腺激素水平变化趋势分析

目的 探讨80岁以上高龄老年人甲状腺激素水平变化趋势.方法 将602例健康志愿者按年龄分为中青年组(20～59岁)226例、老年组(60～79岁)195例和高龄组(80～102岁)181例,采用化学发光法及放射免疫法测定志愿者血清三碘甲状腺原氨酸(TT3)、甲状腺素(TT4)、游离三碘甲状腺原氨酸(FT3)、游离甲状腺素(FT4)、促甲状腺激素(TSH)、反T3(rT3)水平,并以SPSS 13.0进行统计分析.结果 老年组与中青年组比较,血清FT3和TT3降低,差异有统计学意义(t值分别为2.793和3.627,均为P＜0.01);高龄组与中青年组比较,TT3、TT4、FT3、TSH、rT3浓度差异有统计学意义(t值分别为10.930、6.065、15.398、-2.933、-5.643,均为P＜0.01);老年组与高龄组比较,TT3、TT4、FT3、TSH、rT3浓度差异有统计学意义(t值分别为8.382、4.298、11.573、-3.383、-5.148,均为P＜0.01).FT3、TT3、TT4浓度与年龄呈负相关(r值分别为-0.51、-0.39、-0.25,P＜0.01),rT3、TSH浓度与年龄呈正相关(r值分别为0.32、0.12,P＜0.01),FT4与年龄无相关.高龄组高于或低于临床正常参考值范围的阳性发生率,在TT3、TT4、FT3、FT4、TSH、rT3中分别为0、0、13.8%、0、6.6%、21%.结论 随着年龄增长,老年人血清甲状腺激素水平及促甲状腺激素均有改变,特别是80岁及以上高龄老年人,血清FT3、rT3、TSH变化更为明显,建议临床设立老年人不同年龄段的血清甲状腺激素正常参考值范围,以减少假阳性的发生率.

Abstract：

Objective To explore the variation tendency of serum thyroid hormone level in the elderly aged over 80 years.Methods The 602 healthy volunteers were divided into 3 groups by age:young group (20-59 years of age,n= 226),elderly group (60-79 years of age,n= 195),and advanced age group (80-102 years of age,n=181).Fasting blood of all persons was harvested,then the levels of serum total triiodothyroxine (TT3),total thyroxine (TT4),free tri-iodothyronine (FT3),free thyroxine (FT4),thyroid-stimulating hormone (TSH) and reverse tri-iodothyronine (rT3) were determined by chemistry luminescence technique and radioimmunoassay.Statistical analysis was made by the software SPSS 13.0.Results The levels of serum FT3 and TT3 were lower in elderly group than in young group (t=2.793,3.627,P=0.005,0.000).There were significant differences in the levels of serum TT3,TT4,FT3,TSH and rT3 between young group and advanced-age group (t =10.930,6.065,15.398,- 2.933,- 5.643,all P = 0.000),also between elderly group and advanced-age group (t= 8.382,4.298,11.573,-3.383,-5.148,all P＜0.001).The levels of serum FT3,TT3 and TT4 were negatively correlated with age (r=- 0.51,-0.39 and -0.25,respectively,all P＜0.01).And the levels of serum rT3 and TSH showed positive relationships with age (r=0.32,0.12,all P＜0.01).There were no relationships between the level of serum FT4 and age.The positive rate of serum TT3,TT4,FT3,FT4,TSH and rT3 concentration beyond the reference value was 0,0,13.8%,0,6.6% and 21% in advanced-age group,respectively.Conclusions The levels of serum thyroid hormone and thyroid-stimulating hormone change with age.The levels of FT3,rT3 and TSH change obviously in the elderly aged over 80 years.It could reduce the false positive rate in clinical practice if normal reference range for serum thyroid hormone levels in different aged elderly is established.     

不同碘摄入水平对大鼠甲状腺功能影响的实验研究

目的研究不同碘摄入水平对大鼠甲状腺功能的影响。方法将Wistar大鼠分为低碘(LI)组、正常碘(NI)组、5倍、10倍、50倍、100倍高碘(5HI、10HI、50HI、100HI)组,在喂养3、6、12个月后处死,分别检测血清总T4(TT4)、总T3(TT3)、游离T3(FT3)、游离T4(FT4)、反T3(rT3)水平,以及甲状腺组织中T4、T3、rT3水平。结果3个月时血清TT4、FT4、TT3、FT3、rT3以及甲状腺组织中T4、T3、rT3水平,组间比较差异均有统计学意义(F值分别为54．07、67．80、15．51、27．71、19．73、61．51、40．67、53．86,P<0．01);6个月时上述指标组间比较差异均有统计学意义(F值分别为58．80、58．75、19．64、17．22、47．21、46．01、47．22、126．87,P<0．01);12个月时甲状腺组织中T4、T3、rT3水平组间比较差异均有统计学意义(F值分别为20．44、17．69、29．23,P<0．01)。与NI组相比较,LI组血清和甲状腺组织内各激素水平明显降低,而高碘组随着时间的延长和摄入碘量的增加,血清各激素和甲状腺组织内T3水平出现逐渐降低趋势。结论碘缺乏和碘过量均可导致大鼠甲状腺功能低下,而碘缺乏的作用更明显;大鼠对长期高碘摄入比碘缺乏具有更强的耐受性,只有在长期补充过量碘(>50倍正常需要量)才发生甲状腺功能低下。     

THE THYROID FUNCTION IN YOUNG MEN DURING PROLONGED EXERCISE AND THE EFFECT OF ENERGY AND SLEEP DEPRIVATION

Thyroid function has been investigated in 24 young military cadets participating in a 5 d ranger training course with heavy physical exercise, calorie deficiency and deprivation of sleep. The cadets were divided into three groups, each differing in the amount of sleep and food consumption. The serum levels of thyroid hormones (T4, FT4, T3, rT3) and TBG showed a biphasic pattern during the course. Initially there was an increased secretion concomitant with an increased deiodination of T4 to T3 and rT3 mainly due to physical exercise. When the activities lasted for several days without sufficient food supply the thyroid secretion decreased simultaneously with an alteration of the peripheral conversion of T4 to rT3 instead of T3. A significant correlation was found between the changes in total and free thyroxine (r = 0.9) and between the increase in rT3 and decrease in T3 (r = 0.6). TSH decreased during the first day of activities and remained low throughout the course. The TSH response to TRH stimulation was greatly reduced during the course due to physical exercise and calorie deficiency. The present investigation demonstrates that the thyroid function is strongly affected by prolonged physical exercise and a negative energy balance, whereas sleep deprivation does not have any significant influence. The results indicate that the alteration observed is not regulated just by the hypothalamo-pituitary-thyroid-axis alone.     

Thyroid hormone economy in response to extreme cold exposure in healthy factory workers

The effects of cold exposure on serum total T4 (TT4), total T3 (TT3), free T4 (FT4), free T3 (FT3), rT3, TSH, T4-binding globulin (TBG), and T3 resin uptake were investigated in 82 euthyroid factory workers. Twenty-five workers (group 1) were exposed intermittently (approximately 3.5 h daily) to extreme cold (-40 to -20 C) during the 8-h work shift, and 47 (group 2) were exposed to moderate cold (-10 to 8 C) for the entire 8 h. Ten individuals working at room temperature for the same period also were studied. After cold exposure, serum TT4 decreased in group 1 and did not change in group 2, whereas FT4 did not change in group 1 and increased in group 2. After exposure, serum TT3 and rT3 decreased significantly in both groups, while FT3 did not change in either. The basal serum TT4 levels in groups 1 and 2 were significantly lower than those in the control group, whereas those of FT4 and FT3 were higher. Thus, cold exposure had opposite effects on total thyroid hormones and their free fractions, consistent with a cold-induced decrease in thyroid hormone-binding capacity. A postexposure decrease in serum TBG was found in women in group 2, but not in men in either group 2 or group 1, suggesting that factors other than decreased TBG are also involved. The results suggest the possibilities that 1) decreased thyroid hormone-binding capacity is an adaptive response to cold exposure, and/or 2) increased free thyroid hormone levels in response to cold exposure result in a new higher equilibrium between extracellular and intracellular FT4 and FT3.     

Circulating free T3 in pregnancy, liver diseases, diabetes mellitus and thyroid diseases

Measurement of serum concentrations of free triiodothyronine (FT3) is considered to be an accurate index of thyroid function in the patient. In this study, we measured serum concentrations of FT3, free thyroxine (FT4) and reverse triiodothyronine (rT3) by radioimmunoassay in blood samples taken from the navel cord of 20 newborns as well as 20 nonpregnant women, 20 pregnant women, 10 patients with liver diseases, 25 patients with diabetes mellitus, 65 patients with hyperthyroidism, 30 patients with primary hypothyroidism and 29 normal subjects. In pregnant women, serum FT3 and FT4 levels gradually decreased as the pregnancy progressed. In cord blood, FT3 levels were less than a quarter of the values found during the first trimester of pregnancy or that of non-pregnant women, whereas serum rT3 levels were drastically increased. In chronic hepatitis, liver cirrhosis and diabetes mellitus, serum FT3 and FT4 levels were significantly lower than that in the controls. In thyroid diseases, serum FT3 levels varied parallel to other thyroid hormone levels. In primary hypothyroidism, however, serum FT3 levels were still lower than these in the controls after treatment with 1-thyroxine, whereas other thyroid hormone levels and TSH levels returned to control levels.(ABSTRACT TRUNCATED AT 250 WORDS)     

Pituitary-thyroid hormone economy in healthy aging men: basal indices of thyroid function and thyrotropin responses to constant infusions of thyrotropin releasing hormone

In order to assess the effects of aging, as distinct from those of thyroid disease or extrathyroidal illness, on certain indices of thyroid function, we studied 74 healthy, ambulatory men recruited from the Baltimore Longitudinal Study on Aging. We determined basal serum values of T4, T3, rT3, thyroxine-binding globulin (TBG), and T3 resin uptake (T3RU) and calculated the free T4 index (FT4I = T4 X T3RU/100), free T3 index (FT3I = T3 X T3RU/100), and T4/TBG ratio for each subject. We used an ultrasensitive RIA to measure variations in basal concentrations of TSH within the normal range. We then infused TRH at a constant rate (0.4 microgram/min iv) for 240 min into 63 of the same men; serum samples, collected at 15-min intervals during the infusion, were analyzed for TSH by routine RIA. Subjects were divided into 3 groups according to age; A (n = 26, mean age = 39.4), B (n = 23, mean age = 60.0), and C (n = 25, mean age = 79.6). Analysis of variance with Duncan's multiple range test and regression analysis were used to evaluate data. There was no significant (P greater than 0.05) variation with age of basal serum values of T4, TBG, or T3RU. Comparison of groups A and C showed significant decreases of mean values of serum T3 (-11%, P less than 0.05), FT3I (-13%, P = 0.02), FT4I (-11%, P less than 0.01), and T4/TBG ratio (-12%, P less than 0.01) and an increase in serum TSH (+38%, P less than 0.05). For these variables, the mean values for group B were intermediate between, but not significantly different from, those of A and C. Regression analysis showed significant correlations of age with T3, FT3I, FT4I, T4/TBG, and TSH at P levels similar to those obtained by Duncan's test. No elderly individual exhibited a baseline elevation of TSH (greater than 7 microU/ml) or depression of T4 (less than 5 micrograms/dl), suggesting that primary hypothyroidism was not present in our old group. The basal TSH concentration did not correlate significantly with any index of thyroid function except with FT3I in group C (r = -0.43, P less than 0.05). In all age groups the TSH responses to TRH exhibited a biphasic pattern with early and late peaks.(ABSTRACT TRUNCATED AT 400 WORDS)     

Long-term alprenolol treatment affects serum T4, T3 and rT3 in euthyroid patients with ischaemic heart disease

After treatment with alprenolol for 1 year, serum 3,3',5'-triiodothyronine (rT3) was significantly increased (P less than 0.01) in a group (n = 20) of euthyroid subjects compared to a control group (n = 20) given placebo. All subjects had definite or suspected myocardial infarction one year previously. Serum thyroxine (T4), free T3 index (FT4I), serum 3,5,3'-triiodothyronine, (T3) and free T3 index (FT3I) were not significantly different in the two groups. Alprenolol and placebo were gradually withdrawn over 14 days. On the first day after withdrawal a significant decrease in serum rT3 in the alprenolol treated group was the only change observed. Fourteen days after withdrawal a significant fall in serum T4, FT4I, rT3 and a rise in serum T3 and FT3I was found in the alprenolol treated group. Six months after withdrawal the only further change observed in the alprenolol treated group was an increase in T3 and FT3I. No changes occurred in the placebo treated group in any of the hormones studied. The results are consistent with a direct effect of long-term alprenolol treatment on the peripheral levels of serum T4, T3 and rT3 in euthyroid subjects. The changes in the thyroid hormones after withdrawal further indicate withdrawal of a permanent inhibition of 5'deiodinase during long-term treatment with alprenolol in euthyroid subjects.     

Bexarotene-induced hypothyroidism: bexarotene stimulates the peripheral metabolism of thyroid hormones

OBJECTIVE: Therapy with the retinoid X receptor agonist bexarotene is associated with hypothyroidism caused by decreased pituitary TSH secretion. To evaluate the effects of bexarotene on peripheral thyroid hormone metabolism, we performed a study in athyreotic subjects on a fixed substitution dose with L-T4. DESIGN: The design was an open prospective 6-wk intervention study. METHODS: Ten athyreotic patients with pulmonary metastases of differentiated thyroid carcinoma received 6-wk redifferentiation treatment with 300 mg bexarotene/d. L-T4 doses were kept stable. Before and in the sixth week of therapy, serum levels of total T4, free T4 (FT4), T3, reverse T3 (rT3), and TSH were measured. To study nondeiodinase-mediated thyroid hormone degradation, serum levels of T4 sulfate (T4S) were measured. Recombinant human TSH was administered before and in the sixth week of bexarotene therapy. RESULTS: Bexarotene induced profound decreases in total T4 (56% of baseline), FT4 (47%), T3 (69%), rT3 (51%), and T4S (70%) in all patients, whereas TSH levels were not affected. The T3/rT3 ratio increased by 43%, and the T4S/FT4 ratio increased by 48%. Serum TSH levels before and after recombinant human TSH were unaffected by bexarotene. CONCLUSIONS: In the present study, we demonstrate that increased peripheral degradation of thyroid hormones by a nondeiodinase-mediated pathway contributes to bexarotene induced-hypothyroidism.     

Thyroid of lake sturgeon, Acipenser fulvescens. I. Hormone levels in blood and tissues

The authors measured thyroid hormone (TH) levels in plasma, whole carcass, and tissues of cultured 2-year-old immature lake sturgeon held in fresh water and in serum of adults at spawning time from the Winnipeg River. Circulating thyroxine (T4) and 3,5,3'-triiodothyronine (T3) levels were low (T4 approximately 0.3 ng/ml, T3 approximately 0.2 ng/ml) in all cultured fish and most adults, but a few of the latter had exceptionally high T4 and T3 levels. The percentages of blood TH found in erythrocytes were 19.5% (T4), 6.1% (T3) and 6.9% (reverse T3 = rT3). Equilibrium dialysis showed much higher percentages of plasma free (F) FT4 (1.1%), FT3 (0.4%), and FrT3 (3,3',5'-triiodothyronine = rT3, 3.0%) for sturgeon than for rainbow trout, indicating more limited TH binding to sturgeon plasma sites. However, concentrations of FT4 and FT3 were close to those reported for salmonids. T3 levels exceeded T4 levels in most extrathyroidal tissues of cultured sturgeon but in most cases were less than 0.1 ng/g and 10 to 100 times lower than reported for salmonids; only the whole brain T3 concentration (5.6 ng/g) approached that of salmonids. The digested thyroid contained 21.3 ng T3/g and 2.4 ng T4/g. The authors conclude that lake sturgeon have a low circulating reserve of bound TH but have FT4 and FT3 concentrations close to those of salmonids. The high thyroidal T3:T4 ratio and low tissue T4 levels suggest that, in contrast to teleosts studied to date, the thyroid may be a significant direct source of T3, the primary TH in sturgeon tissues. High serum T4 and T3 levels in some sturgeon at spawning time may suggest a thyroid role in reproduction.     

Thyroid function in physiological aging and in centenarians: possible relationships with some nutritional markers.

Changes in thyroid function are often described in elderly subjects; however, their pathophysiologic significance and the possible contributory role of both malnutrition and nonthyroidal illness are still debated. The aim of this cross-sectional study was to investigate thyroid function in relationship to some markers of the nutritional status in a group of healthy old subjects and in some centenarians living in nursing homes. Patients included 24 clinically healthy elderly women (age, 71 to 93 years), 24 clinically healthy centenarian women (age, 100 to 106 years), and 20 healthy young subjects (age, 22 to 33 years). Blood samples were drawn from each subject for the evaluation of thyroid-stimulating hormone (TSH), free triiodothyronine (FT(3)), free thyroxine (FT(4),) reverseT(3) (rT3), autoantibodies against thyroglobulin (AbTg) and against thyroid peroxidase (AbTPO), and for the main humoral nutritional markers. TSH and thyroid hormones were assayed by fluoroimmunometric method; rT3 and thyroid autoantibodies by radioimmunoassay (RIA) and enzyme chemiluminescent immunometric assay, respectively. The mean values of TSH, FT(3) and FT(4) fell within the normal range in both groups. However, by comparison to old controls, in centenarian subjects, TSH levels were significantly lower, whereas rT(3) concentrations were slightly, but significantly, increased. Autoantibodies positivity was found in 4.16% of centenarians and in 10.4% and 13.6% of old and young controls. Thus, the incidence of thyroid autoantibodies was lower in centenarians than in old controls. Except for transferrin, lower than the normal range in centenarians, all of the other nutritional markers evaluated fell within the laboratory range of normality. Total cholesterol levels were significantly reduced in centenarians by comparison to old controls. Our results showed an age-related decline of the TSH levels and a significant increase of the rT(3) concentrations in centenarians by comparison to old controls. These findings may be related to an age-dependent reduction of the 5'-deiodinase activity rather than to important changes of nutritional markers.     

Clinical study on thyroid hormone levels in tuberculous patients]

The article reported the results of serum total thyroxine (TT4), triiodothyronine (TT3), reverse triiodothyronine (rT3), triiodothyronine resin uptake ratio (T3RU) thyroid stimulating hormone (TSH), free thyroxine index (FT4I), and ratio of T3/rT3 in 103 tuberculous patients. The results showed the levels of serum TT4, TT3 and ratio T3/rT3 in tuberculous patients were lower than those of 50 healthy subjects (total P less than 0.01), rT3, T3RU and TSH were higher than those (total P less than 0.01). FT4I has no significant difference between the two groups (P greater than 0.05).     

The effect of genetic variation in the type 1 deiodinase gene on the interindividual variation in serum thyroid hormone levels: an investigation in healthy Danish twins

Introduction  Genetic factors have a considerable influence on serum thyroid hormone levels. The C785T and A1814G polymorphisms, located in the 3' untranslated region of the type 1 deiodinase (D1) gene have been associated with serum FT4 and rT3 levels.
Objective  In healthy Danish twins, we examined the association of these polymorphisms with serum thyroid hormone levels and determined the proportion of genetic influence explained by these variants. We analysed the underlying functional mechanism by performing mRNA stability measurements and analysed the effect of these variants on D1 activity.
Methods  Serum thyroid measurements and genotypes of the D1-C785T and D1-A1814G polymorphisms were determined in 1192 twins. Structural equation modelling was used to determine heritability estimates. Functional analyses were carried out in D1-transfected JEG3 cells.
Results  Carriers of the D1-785T allele had 3·8% higher FT4 and 14·3% higher rT3 levels, resulting in a lower T3/T4 and T3/rT3 ratio and a higher rT3/T4 ratio. This polymorphism explained 0·87% and 1·79%, respectively, of the variation in serum FT4 and rT3. The D1-A1814G polymorphism was not associated with serum thyroid hormone levels. No differences in D1 mRNA decay rate or D1 activity were observed between wild-type D1 and the two variants.
Conclusion  The D1-C785T polymorphism is consistently and significantly associated with serum thyroid hormone levels. However, the proportion of genetic influence explained by this particular polymorphism is small. No effect of the polymorphism on D1 mRNA decay rate or D1 activity was observed. The underlying functional mechanism needs to be elucidated.     

Euthyroid sick syndrome in meningococcal sepsis: the impact of peripheral thyroid hormone metabolism and binding proteins

CONTEXT AND OBJECTIVES: The objective of this study was to elucidate the influence of disease severity, deiodination, sulfation, thyroid hormone binding, and dopamine use on thyroid function in euthyroid sick syndrome. SETTING: The study was performed at a university-affiliated pediatric intensive care unit (PICU). DESIGN: This was an observational cohort study. PATIENTS: Sixty-nine children with meningococcal sepsis were studied. MAIN OUTCOME MEASURES: Differences in thyroid function among nonsurvivors, shock survivors, and sepsis survivors on PICU admission were the main outcome measures. RESULTS: The main study group consisted of 45 non-dopamine-treated children. All children had decreased total T3 (TT3)/rT3 ratios without elevated TSH. T4 sulfate levels were decreased in 88%. Nonsurvivors had paradoxically higher TT3/rT3 ratios than shock survivors (0.71 vs. 0.30); this ratio also correlated with shorter duration of disease (r = -0.43). TT4 and T4-binding globulin (TBG) levels declined with increasing disease severity. TBG levels correlated inversely with elastase levels (r = -0.46). Only TSH levels were significantly lower in 24 dopamine-treated children compared with non-dopamine-treated children (0.65 vs. 0.84), whereas other thyroid hormones did not significantly differ. Both higher TT3/rT3 ratios and lower TT4 levels were predictive for mortality, but this disappeared when IL-6 was entered into the regression model. CONCLUSIONS: All children with meningococcal sepsis showed signs of euthyroid sick syndrome. Alterations in peripheral thyroid hormone metabolism related inversely to the duration of disease and seemed to be enacted by profound induction of type 3 deiodinase rather than by down-regulation of type 1. Lower TT4 levels were related to increased turnover of TBG by elastase. Dopamine was found to suppress only TSH secretion, not other thyroid hormone levels, on PICU admission. Both the TT3/rT3 ratio and TT4 levels were predictive for mortality, but were not superior to IL-6.