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Lin W, Jia S, Chen Y, Shi H, Zhao J, Li Z, Wu Y, Jiang H, Zhang Q, Wang W, Chen Y, Feng C, Xia S. Korotkoff sounds dynamically reflect changes in cardiac function based on deep learning methods. Front Cardiovasc Med 2022; 9:940615. [PMID: 36093170 PMCID: PMC9458936 DOI: 10.3389/fcvm.2022.940615] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2022] [Accepted: 07/18/2022] [Indexed: 11/24/2022] Open
Abstract
Korotkoff sounds (K-sounds) have been around for over 100 years and are considered the gold standard for blood pressure (BP) measurement. K-sounds are also unique for the diagnosis and treatment of cardiovascular diseases; however, their efficacy is limited. The incidences of heart failure (HF) are increasing, which necessitate the development of a rapid and convenient pre-hospital screening method. In this review, we propose a deep learning (DL) method and the possibility of using K-methods to predict cardiac function changes for the detection of cardiac dysfunctions.
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Affiliation(s)
- Wenting Lin
- Department of Cardiology, The Fourth Affiliated Hospital, Zhejiang University School of Medicine, Yiwu, China
| | - Sixiang Jia
- Department of Cardiology, The Fourth Affiliated Hospital, Zhejiang University School of Medicine, Yiwu, China
| | - Yiwen Chen
- Department of Cardiology, The Fourth Affiliated Hospital, Zhejiang University School of Medicine, Yiwu, China
| | - Hanning Shi
- Department of Anime and Comics, Hangzhou Normal University, Hangzhou, China
| | - Jianqiang Zhao
- Department of Cardiology, The Fourth Affiliated Hospital, Zhejiang University School of Medicine, Yiwu, China
| | - Zhe Li
- Department of Cardiology, The Fourth Affiliated Hospital, Zhejiang University School of Medicine, Yiwu, China
| | - Yiteng Wu
- Department of Cardiology, The Fourth Affiliated Hospital, Zhejiang University School of Medicine, Yiwu, China
| | - Hangpan Jiang
- Department of Cardiology, The Fourth Affiliated Hospital, Zhejiang University School of Medicine, Yiwu, China
| | - Qi Zhang
- Department of Cardiology, The Fourth Affiliated Hospital, Zhejiang University School of Medicine, Yiwu, China
| | - Wei Wang
- Department of Cardiology, The Fourth Affiliated Hospital, Zhejiang University School of Medicine, Yiwu, China
| | - Yayu Chen
- Department of Cardiology, The Fourth Affiliated Hospital, Zhejiang University School of Medicine, Yiwu, China
| | - Chao Feng
- Department of Cardiology, The Fourth Affiliated Hospital, Zhejiang University School of Medicine, Yiwu, China
| | - Shudong Xia
- Department of Cardiology, The Fourth Affiliated Hospital, Zhejiang University School of Medicine, Yiwu, China
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Yoon SA, Chang YS, Yang M, Ahn SY, Sung SI, Cho HS, Park WS. Effect of levothyroxine supplementation in extremely low birth weight infants with transient hypothyroxinemia of prematurity. Sci Rep 2022; 12:9717. [PMID: 35690687 PMCID: PMC9188355 DOI: 10.1038/s41598-022-13927-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2022] [Accepted: 05/30/2022] [Indexed: 11/09/2022] Open
Abstract
This study aimed to determine the short- and/or long-term outcomes of levothyroxine replacement therapy in extremely low birth weight (ELBW) infants with transient hypothyroxinemia of prematurity (THOP). The medical records of 335 ELBW infants with THOP were reviewed retrospectively to identify whether levothyroxine treatment affects short- and/or long-term outcomes at a corrected age of 2 years. The infants were arbitrarily grouped based on thyroxine (T4) (free T4 [fT4]) levels into group 1 (n = 142), which included infants with T4 (fT4) levels < 2.5 (0.5) ng/dl, and group 2 (n = 193), which included those with T4 (fT4) levels ranging from ≥ 2.5 (0.5) ng/dl to < 4.5 (0.9) ng/dl. Levothyroxine replacement therapy was not associated with beneficial short- or long-term outcomes in ELBW infants with THOP. Short-term outcomes, such as mortality and composite morbidities, and long-term outcomes, such as failure to achieve catch-up height at a corrected age of 2 years, were significantly higher in group 1 than in group 2, regardless of levothyroxine treatment status. Levothyroxine replacement therapy is not associated with short-or long-term advantages in ELBW infants with THOP. This study suggests that the severity of THOP may be the major determinant of adverse outcomes in ELBW infants with THOP, rather than levothyroxine treatment.
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Affiliation(s)
- Shin Ae Yoon
- Department of Pediatrics, Chungbuk National University Hospital, Chungbuk National University School of Medicine, 1 Sunhwan-ro 776, Seowon-gu, Cheongju, 28644, South Korea
| | - Yun Sil Chang
- Department of Pediatrics, Samsung Medical Center, Sungkyunkwan University School of Medicine, 81 Irwon-Ro, Gangnam-gu, Seoul, 06351, South Korea
| | - Misun Yang
- Department of Pediatrics, Samsung Medical Center, Sungkyunkwan University School of Medicine, 81 Irwon-Ro, Gangnam-gu, Seoul, 06351, South Korea
| | - So Yoon Ahn
- Department of Pediatrics, Samsung Medical Center, Sungkyunkwan University School of Medicine, 81 Irwon-Ro, Gangnam-gu, Seoul, 06351, South Korea
| | - Se In Sung
- Department of Pediatrics, Samsung Medical Center, Sungkyunkwan University School of Medicine, 81 Irwon-Ro, Gangnam-gu, Seoul, 06351, South Korea
| | - Hee-Seung Cho
- Department of Pediatrics, Samsung Medical Center, Sungkyunkwan University School of Medicine, 81 Irwon-Ro, Gangnam-gu, Seoul, 06351, South Korea
| | - Won Soon Park
- Department of Pediatrics, Samsung Medical Center, Sungkyunkwan University School of Medicine, 81 Irwon-Ro, Gangnam-gu, Seoul, 06351, South Korea.
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Incidence and severity of transient hypothyroxinaemia of prematurity associated with survival without composite morbidities in extremely low birth weight infants. Sci Rep 2019; 9:9628. [PMID: 31270383 PMCID: PMC6610124 DOI: 10.1038/s41598-019-46108-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Accepted: 05/07/2019] [Indexed: 11/18/2022] Open
Abstract
This study investigated the incidence of transient hypothyroxinaemia of prematurity (THOP) associated with survival without composite morbidities and the predictability of THOP severity in extremely low birth weight infants (ELBWIs). We retrospectively reviewed the medical records of 546 ELBWIs who underwent initial thyroid function tests within 14 postnatal days, with 156 ELBWIs from 2000 to 2005 (period I) and 390 from 2006 to 2013 (period II). The infants were stratified into 23–24, 25–26 and 27–28 weeks’ gestation subgroups within each period; the initial thyroxine (T4) level, mortality, clinical characteristics and composite morbidities, including bronchopulmonary dysplasia, intraventricular haemorrhage, necrotizing enterocolitis, and retinopathy of prematurity were analysed. The predictive value of the initial T4 level, Apgar score at 5 min, and clinical risk index for babies II (CRIB II) score for estimating mortality and survival with or without composite morbidities was assessed. Comparing period II and period I, the incidence of THOP was significantly decreased along with significantly increased survival without composite morbidities in ELBWIs at 25–28 weeks’ gestation. The severity of THOP showed significant associations with mortality and composite morbidities. The initial T4 level was most effective for predicting outcome compared with Apgar and CRIB II scores.
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Thyroid and food: a Mediterranean perspective. MEDITERRANEAN JOURNAL OF NUTRITION AND METABOLISM 2012. [DOI: 10.1007/s12349-012-0095-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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Kaptein EM, Beale E, Chan LS. Thyroid hormone therapy for obesity and nonthyroidal illnesses: a systematic review. J Clin Endocrinol Metab 2009; 94:3663-75. [PMID: 19737920 DOI: 10.1210/jc.2009-0899] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
CONTEXT Thyroid hormone therapy to enhance weight loss in obesity during caloric deprivation and to improve morbidity and mortality in adults with nonthyroidal illnesses remains controversial. OBJECTIVE The aim of this study was to conduct a systematic review evaluating effectiveness and risks of T(3) and/or T(4) therapy in these populations. DATA SOURCES Electronic databases and reference lists were searched. STUDY SELECTION Studies with comparable control groups comparing T(3) and/or T(4) therapy to placebo in randomized controlled trials (RCTs) or prospective observational studies were selected. DATA EXTRACTION Three reviewers performed serial abstraction. DATA SYNTHESIS During caloric deprivation of obese subjects, T(3) therapy decreased serum TSH and T(4) concentrations. Consistent effects of T(3) or T(4) on weight loss, protein breakdown, metabolic rate, and heart rate could not be established. In euthyroid cardiac patients, T(3) decreased TSH and free T(4) levels, without consistent effects of T(3) or T(4) on heart rate, cardiac output, or systemic vascular resistance. Mortality increased 3.3-fold with T(4) therapy in acute renal failure patients, whereas an effect in cardiac, critically ill, and burn patients could not be established. Equivalence testing indicated that larger RCTs are required to determine whether thyroid hormone therapy alters end-points in obesity or nonthyroidal illnesses. LIMITATIONS Numbers of usable unique studies were small, numbers of patients in each study were inadequate, end-points were variable, few RCTs were performed, and study quality of non-RCTs was poor. CONCLUSIONS Available data are inconclusive regarding effectiveness of thyroid hormone therapy in treating obesity or nonthyroidal illnesses, whereas data support that such therapy induces subclinical hyperthyroidism.
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Affiliation(s)
- Elaine M Kaptein
- Department of Medicine, University of Southern California, Los Angeles, California 90033, USA.
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Gastaldi G, Russell A, Golay A, Giacobino JP, Habicht F, Barthassat V, Muzzin P, Bobbioni-Harsch E. Upregulation of peroxisome proliferator-activated receptor gamma coactivator gene (PGC1A) during weight loss is related to insulin sensitivity but not to energy expenditure. Diabetologia 2007; 50:2348-55. [PMID: 17828388 DOI: 10.1007/s00125-007-0782-1] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/29/2007] [Accepted: 06/22/2007] [Indexed: 12/26/2022]
Abstract
AIMS/HYPOTHESIS We investigated whether skeletal muscle peroxisome proliferator-activated receptor gamma coactivator-1 (PGC1A; also known as PPARGC1A) and its target mitofusin-2 (MFN2), as well as carnitine palmitoyltransferase-1 (CPT1; also known as carnitine palmitoyltransferase 1A [liver] [CPT1A]) and uncoupling protein (UCP)3, are involved in the improvement of insulin resistance and/or in the modification of energy expenditure during surgically induced massive weight loss. MATERIALS AND METHODS Seventeen morbidly obese women (mean BMI: 45.9 +/- 4 kg/m(2)) were investigated before, and 3 and 12 months after, Roux-en-Y gastric bypass (RYGB). We evaluated insulin sensitivity by the euglycaemic-hyperinsulinaemic clamp, energy expenditure and substrate oxidation by indirect calorimetry, and muscle mRNA expression by PCR. RESULTS Post-operatively, PGC1A was enhanced at 3 (p = 0.02) and 12 months (p = 0.03) as was MFN2 (p = 0.008 and p = 0.03 at 3 and 12 months respectively), whereas UCP3 was reduced (p = 0.03) at 12 months. CPT1 did not change. The expression of PGC1A and MFN2 were strongly (p < 0.0001) related. Insulin sensitivity, which increased after surgery (p = 0.002 at 3, p = 0.003 at 12 months), was significantly related to PGC1A and MFN2, but only MFN2 showed an independent influence in a multiple regression analysis. Energy expenditure was reduced at 3 months post-operatively (p = 0.001 vs before RYGB), remaining unchanged thereafter until 12 months. CPT1 and UCP3 were not significantly related to the modifications of energy expenditure or of lipid oxidation rate. CONCLUSIONS/INTERPRETATION Weight loss upregulates PGC1A, which in turn stimulates MFN2 expression. MFN2 expression significantly and independently contributes to the improvement of insulin sensitivity. UCP3 and CPT1 do not seem to influence energy expenditure after RYGB.
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Affiliation(s)
- G Gastaldi
- Service of Therapeutic Education for Chronic Diseases, Geneva University Hospital, 24, Rue Micheli du Crest, 1211 Geneva, Switzerland
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Abstract
Thyroid hormones are required for normal development of the brain. Transient hypothyroxinaemia is the most common thyroid dysfunction in preterm infants and is defined by temporary low levels of T4, T3 and normal or low TSH. Low T4 levels in preterm infants are associated with persistent neurodevelopmental deficits in cognitive and motor function. Thyroid hormone substitution trials to date are underpowered and show inconsistent results; the question remains -- are low T4 levels simply an epiphenomenon? The aetiology of transient hypothyroxinaemia is multifactorial and the components amenable to correction form the basis of the therapeutic strategy: rectification of iodine deficiency in parenteral nutrition; a reduction of non-thyroidal illnesses and attenuation of their severity; and substitution of drugs that interfere with the hypothalamic-pituitary-thyroid axis. Thyroxine substitution therapy should only be done in the context of clinical trials and only in those infants who are hypothyroxinaemic.
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De Groot LJ. Non-thyroidal illness syndrome is a manifestation of hypothalamic-pituitary dysfunction, and in view of current evidence, should be treated with appropriate replacement therapies. Crit Care Clin 2006; 22:57-86, vi. [PMID: 16399020 DOI: 10.1016/j.ccc.2005.10.001] [Citation(s) in RCA: 97] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
This article documents the role of hypothalamic hypothyroidism and decreased T4-->T3 conversion as the cause of low T4 and T3 in non-thyroidal illness syndrome (NTIS). This article also presents the arguments for administration of replacement triiodothyronine (T3) and thyroxine (T4) hormone in patients who have NTIS. It is impossible to be certain at this time that it is beneficial to replace hormone, or whether this could be harmful. Only a prospective study will be adequate to prove this point, and probably this would need to involve hundreds of patients. If effective, thyroid hormone replacement will be one of many beneficial treatments given the patient, rather than a single magic bullet, which would reverse all the metabolic changes going wrong in these severely ill patients.
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Affiliation(s)
- Leslie J De Groot
- Endocrine Division, Brown University, Box G, Room E-308, 70 Ship Street, Providence, RI 02920, USA.
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Affiliation(s)
- L J De Groot
- Thyroid Study Unit, University of Chicago, Illinois 60637, USA
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Rone JK, Dons RF, Reed HL. The effect of endurance training on serum triiodothyronine kinetics in man: physical conditioning marked by enhanced thyroid hormone metabolism. Clin Endocrinol (Oxf) 1992; 37:325-30. [PMID: 1483287 DOI: 10.1111/j.1365-2265.1992.tb02332.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
OBJECTIVE We studied the relationship between endurance training, aerobic capacity, and T3 metabolism in healthy euthyroid men. DESIGN T3 kinetic studies performed on two groups of subjects differentiated on the basis of physical activity status and aerobic capacity. SUBJECTS Five endurance-trained athletes and five sedentary controls (mean +/- SD VO2 max = 48.2 +/- 7.1 vs 23.2 +/- 4.5 ml/kg/min, respectively) matched for age, body surface area, lean body mass, and baseline thyroid function. MEASUREMENTS Kinetic analysis performed using serial serum T3 levels measured following oral T3 administration. Metabolic clearance rate, total volume of distribution, disposal rate, and total body pool calculated using non-compartmental analysis. RESULTS When normalized for lean body mass, all kinetic parameters were 25-38% greater in the athletic group compared to controls (P < 0.05). Total volume of distribution, disposal rate, and total body pool were positively correlated with aerobic capacity (r = +0.69 to +0.79; P < 0.05). Metabolic clearance rate was positively correlated to a non-significant degree. CONCLUSIONS These results confirm the findings of prior studies that thyroid hormone metabolism is altered by physical conditioning. In addition, we demonstrated a positive correlation between aerobic capacity and several parameters of T3 kinetics. Differences in absolute lean body mass cannot explain these findings; rather it appears that there is something qualitatively different in the way endurance-trained tissue processes thyroid hormone, compared to untrained tissue. The study was not designed to elucidate these differences at the cellular level; however, it does support a link between muscle physiology and T3 activity and may suggest a physiological role for thyroid hormone in physical conditioning.
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Affiliation(s)
- J K Rone
- Department of Endocrinology & Metabolism, Wilford Hall USAF Medical Center, Lackland Air Force Base, Texas
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Marine N, Hershman JM, Maxwell MH, Dornfeld LP, Schroth P. Dietary restriction on serum thyroid hormone levels. Am J Med Sci 1991; 301:310-3. [PMID: 2021153 DOI: 10.1097/00000441-199105000-00003] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
To determine the long term effects of a protein sparing fast on serum thyroid hormone levels, the authors studied 38 obese patients ingesting a diet of 320 kcal for up to 13 weeks. The high baseline serum triiodothyronine (T3) levels decreased significantly by the first week, further decreased by the third week, and this lower level persisted for the duration of the fast until realimentation. Serum free T3 index followed the same general pattern as did serum T3 levels. Serum reverse T3 increased significantly by the first week, but by week three, the reverse T3 level had begun to fall, although still significantly increased above baseline. By week seven, reverse T3 had decreased to almost baseline and remained not significantly changed from the baseline to 13 weeks. Serum thyroxine (T4) increased significantly by the first week in all patients, but by the third week had returned to baseline levels which persisted to 13 weeks. The free T4 index and free T4 concentrations showed the same increment at week one and then returned to baseline levels. There were no significant changes in serum thyroxine-binding globulin (TBG) or thyroid-stimulating hormone (TSH) concentrations. The changes in serum T3 and reverse T3 levels are attributable to alterations in peripheral 5'-monodeiodination of T4 and reverse T3 induced by the protein sparing fast.
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Affiliation(s)
- N Marine
- Endocrine Research Laboratory, Wadsworth Veterans Administration Medical Center, Los Angeles, CA 90073
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Strickland SS, Ulijaszek SJ. Energetic cost of standard activities in Gurkha and British soldiers. Ann Hum Biol 1990; 17:133-44. [PMID: 2334108 DOI: 10.1080/03014469000000882] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Measurements of basal metabolic rate and energy expenditure at lying, sitting, standing, and performing a step test at four levels of exercise, were made on Gurkha soldiers stationed in Britain and on British controls matched by body weight and occupational background. There was no significant difference in basal metabolic rate (BMR), nor in the energy cost of lying, sitting and standing between the two groups. Gurhas showed significantly lower gross and net energy expenditure, and so significantly greater net mechanical efficiency, at the lower levels of step exercise. The ratio of gross energy expenditure to BMR was lower in Gurkhas at the lowest rates of stepping compared with the British controls. These results suggest that the energy cost of some physical activities expressed as multiples of BMR may not be constant across populations.
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Affiliation(s)
- S S Strickland
- Department of Public Health and Policy, London School of Hygiene, UK
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Welle SL, Campbell RG. Decrease in resting metabolic rate during rapid weight loss is reversed by low dose thyroid hormone treatment. Metabolism 1986; 35:289-91. [PMID: 3959900 DOI: 10.1016/0026-0495(86)90142-3] [Citation(s) in RCA: 35] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
In order to determine if reduced serum T3 concentrations contribute to the decrease in resting metabolic rate (RMR) during rapid weight loss, we administered T3 (30 micrograms/d) and T4 (100 micrograms/d) to obese subjects receiving a very low energy diet to reverse a decrease in serum thyroid hormone concentrations. During the first two weeks of weight loss, before thyroid hormone replacement, the mean RMR of five obese subjects declined to 86% of the baseline level as the mean serum T3 concentration decreased to 72% of the baseline level. Thyroid hormone replacement for one week, while the low energy diet continued, increased the mean RMR to 94% of the baseline level while increasing mean serum T3 and T4 concentrations to approximately 130% of the baseline level. A second week of thyroid treatment caused no further change in RMR. These data suggest that reduced serum T3 concentrations contribute to the decrease in RMR during rapid weight loss. However, the regimen of thyroid hormone replacement employed did not completely restore a normal RMR in obese subjects on a very low energy diet, in spite of elevating serum thyroid hormone concentrations slightly above weight-maintenance levels.
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Kaptein EM, Fisler JS, Duda MJ, Nicoloff JT, Drenick EJ. Relationship between the changes in serum thyroid hormone levels and protein status during prolonged protein supplemented caloric deprivation. Clin Endocrinol (Oxf) 1985; 22:1-15. [PMID: 3978824 DOI: 10.1111/j.1365-2265.1985.tb01059.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The relationship between the changes in serum thyroid hormone levels and nitrogen economy during caloric deprivation were investigated in ten obese men during a 40 d, 400 kcal protein-supplemented weight-reducing diet. This regimen induced increases in the serum levels of total T4, free T4 and total rT3, and decreases of total T3, while serum TSH remained unchanged. There were progressive decreases in total body weight and urinary losses of total nitrogen and 3-methylhistidine, with the early negative nitrogen balance gradually returning towards basal values during the 40 days. Subjects with the largest weight loss had the most increase in the serum levels of total T4 and free T4 index and the greatest decrease in T3. The magnitude of the increase of the nitrogen balance from its nadir was correlated with the extent of the reduction of T3 and increase of T3 uptake ratio and free T4 levels. The decrease in the urinary excretion of 3-methylhistidine correlated with the increase in free T4 and rT3 levels. Nadir serum transferrin values were directly related to peak rT3 values, and the lowest albumin concentrations occurred in subjects with the highest total T4 and free T4 index values. Further, the maximum changes in the serum thyroid hormone levels preceded those of the nutritional parameters. These relationships suggest that: (1) increases in serum rT3 and free T4 and reductions in T3 concentrations during protein supplemented weight reduction may facilitate conservation of visceral protein and reduce muscle protein turnover; and (2) the variation in the magnitude of these changes may account for the heterogeneity of nitrogen economy.
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