Relationship Between Thyrotropin and Body Mass Index in Euthyroid Subjects

Abstract

Background: Several studies have reported that thyrotropin (TSH) levels are slightly increased in obese subjects. On the contrary, other studies have provided no evidence for an association between thyroid status and body mass index (BMI).

Aim: Our aim has been to evaluate the relationship between TSH and BMI in a group of subjects with obesity, overweight and normal weight with serum TSH levels within the reference range, excluding subjects with hypothyroidism and hyperthyroidism.

Subjects and methods: We evaluated a cohort of 778 euthyroid subjects (488 women, mean age 58.5±15.9 yr) with TSH values between 0.4 and 5.0 mU/l. There were 321 subjects with obesity (BMI≥30 kg/m²), 319 with overweight (25–29.9 kg/m²) and 138 with normal weight (18.5–24.9 kg/m²).

Results: Serum TSH levels significantly increased with weight category in studied subjects (normal weight, median [interquartile range], 1.24 [0.94–1.72]; overweight, 1.31 [1.00–1.93]; obesity, 1.66 [1.15–2.44] mU/l; P<0.001). Free thyroxine (T4) was not statistically different in subjects within the 3 weight categories. A significant correlation was found between TSH and BMI (r=0.217, P<0.001). Subjects with serum TSH levels in the upper tertile (1.84–5.0 mU/l) exhibited a BMI value (30.8 [26.9–34.9] kg/m²) significantly higher (P<0.001) than that found in subjects with TSH levels in the middle (1.13–1.83 mU/l, 28.8 [25.8–32.3] kg/m²) or in the lower tertile (0.4–1.12 mU/l, 27.4 [25.4–30.6] kg/m²). There were no differences in BMI in patients classified according to tertiles of free T4. However, when studying a subgroup of patients with negative thyroid autoimmunity (n=375), we could not observe any significant difference in TSH levels between obese (n=106, 1.24 [0.90–1.81] mU/l) and non-obese subjects (n=269, 1.23 [0.90–1.80] mU/l). No correlation was found between TSH and BMI in this subgroup of subjects with negative thyroid autoimmunity (r=−0.035, NS).

Conclusion: These results suggest that the relationship between TSH and BMI observed in euthyroid subjects is lost when subjects with negative autoimmunity are selected.

Key words

thyrotropin - body mass index - thyroid function - obesity

References

• 1 Iglesias P, Alvarez Fidalgo P, Codoceo R. et al . Serum concentrations of adipocytokines in patients with hyperthyroidism and hypothyroidism before and after control of thyroid function.  Clin Endocrinol (Oxf). 2003;  59 621-629
• 2 Matzen LE, Kventny J, Pedersen KK. TSH, thyroid hormones and nuclear-binding of T3 in mononuclear blood cells form obese and nonobese women.  Scand J Clin Lab Invest. 1989;  49 249-253
• 3 Stichel H, l’Allemand D, Grüters A. Thyroid function and obesity in children and adolescents.  Horm Res. 2000;  54 14-19
• 4 Iacobellis G, Ribaudo MC, Zappaterreno A. et al . Relationship of thyroid function with body mass index, leptin, insulin sensitivity and adiponectin in euthyroid obese women.  Clin Endocrinol (Oxf). 2005;  62 487-491
• 5 Reinehr T, de Sousa G, Andler W. Hyperthyrotropinemia in obese children is reversible after weight loss and is not related to lipids.  J Clin Endocrinol Metab. 2006;  91 3088-3091
• 6 Bastemir M, Akin F, Alkis E. et al . Obesity is associated with increased serum TSH levels, independent of thyroid function.  Swiss Med Wkly. 2007;  137 431-434
• 7 Reinehr T, Isa A, de Sousa G. et al . Thyroid hormones and their relationship to weight status.  Horm Res. 2008;  70 51-57
• 8 Rotondi M, Leporati P, La Manna A. et al . Raised serum TSH levels in patients with morbid obesity: is it enough to diagnose subclinical hypothyroidism?.  Eur J Endocrinol. 2009;  160 403-408
• 9 Moulin de Moraes CM, Mancini MC, de Melo ME. et al . Prevalence of subclinical hypothyroidism in a morbidly obese population and improvement after weight loss induced by Roux-en-Y gastric bypass.  Obes Surg. 2005;  15 1287-1291
• 10 Michalaki MA, Vagenakis AG, Leonardou AS. et al . Thyroid function in humans with morbid obesity.  Thyroid. 2006;  16 73-78
• 11 Knudsen N, Laurgerg P, Rasmussen LB. et al . Small differences in thyroid function may be important for body mass index and the occurrence of obesity in the population.  J Clin Endocrinol Metab. 2005;  90 4019-4024
• 12 Nyrnes A, Jorde R, Sundsfjord J. Serum TSH is positively associated with BMI.  Int J Obes (Lond). 2006;  30 100-105
• 13 Gussekloo J, van Exel E, de Craen AJ. et al . Thyroid status, disability and cognitive function, and survival in old age.  JAMA. 2004;  292 2591-2599
• 14 Lindeman RD, Romero LJ, Schade DS. et al . Impact of subclinical hypothyroidism on serum total homocysteine concentrations, the prevalence of coronary heart disease (CHD), and CHD risk factors in the New Mexico Elder Health Survey.  Thyroid. 2003;  13 595-600
• 15 Strata A, Ugolotti G, Contini C. et al . Thyroid and obesity: survey of some function tests in large obese population.  Int J Obes. 1978;  2 333-340
• 16 Duntas L, Hauner H, Rosenthal J. et al . Thyrotropin releasing hormone (TRH) immunoreactivity and thyroid function in obesity.  Int J Obes. 1991;  15 83-87
• 17 Hak AE, Pols HA, Visser TJ. et al . Subclinical hypothyroidism is an independent risk factor for atherosclerosis and myocardial infarction in elderly women: the Rotterdam Study.  Ann Intern Med. 2000;  132 270-278
• 18 Manji N, Boelaert K, Sheppard MC. et al . Lack of association between serum TSH or free T4 and body mass index in euthyroid subjects.  Clin Endocrinol (Oxf). 2006;  64 125-128
• 19 Caraccio N, Ferrannini E, Monzani F. Lipoprotein profile in subclinical hypothyroidism: response to levothyroxine replacement, a randomized placebo-controlled study.  J Clin Endocrinol Metab. 2002;  87 1533-1538
• 20 Perez A, Cubero JM, Sucunza N. et al . Emerging cardiovascular risk factors in subclinical hypothyroidism: lack of change after restoration of euthyroidism.  Metabolism. 2004;  53 1512-1515
• 21 Sociedad Española para el Estudio de la Obesidad (SEEDO) . Consenso SEEDO’2000 para la evaluación del sobrepeso y la obesidad y el establecimiento de criterios de intervención terapéutica.  Med Clín (Barc). 2000;  115 587-597
• 22 Pinkney JH, Goodrick SJ, Katz J. et al . Leptin and the pituitary-thyroid axis: a comparative study in lean, obese, hypothyroid and hyperthyroid subjects.  Clin Endocrinol (Oxf). 1998;  49 583-588
• 23 Reinehr T. Obesity and thyroid function.  Mol Cell Endocrinol. 2010;  316 165-171
• 24 Flier JS, Harris M, Hollenberg AN. Leptin, nutrition, and the thyroid: the why, the wherefore, and the wiring.  J Clin Invest. 2000;  105 859-861
• 25 Zimmermann-Belsing T, Brabant G, Holst JJ. et al . Circulating leptin and thyroid dysfunction.  Eur J Endocrinol. 2003;  149 257-271
• 26 Winter WE, Signorino MR. Molecular thyroidology.  Ann Clin Lab Sci. 2001;  31 221-244
• 27 Chikunguwo S, Brethauer S, Nirujogi V. et al . Influence of obesity and surgical weight loss on thyroid hormone levels.  Surg Obes Rel Dis. 2007;  3 631-635
• 28 Gray RS, Borsey DQ, Seth J. et al . Prevalence of subclinical thyroid failure in insulin-dependent diabetes.  J Clin Endocrinol Metab. 1980;  50 1034-1037
• 29 Perros P, McCrimmon RJ, Shaw G. et al . Frequency of thyroid dysfunction in diabetic patients: value of annual screening.  Diabet Med. 1995;  12 622-627
• 30 Kordonouri O, Klinghammer A, Lang EB. et al . DPV-Initiative of the German Working Group for Pediatric Diabetology. Thyroid autoimmunity in children and adolescents with type 1 diabetes.  Diabetes Care. 2002;  25 1346-1350
• 31 Smithson MJ. Screening for thyroid dysfunction in a community population of diabetic patients.  Diabet Med. 1998;  15 148-150
• 32 Santini F, Pinchera A, Marsili A. et al . Lean body mass is a major determinant of levothyroxine dosage in the treatment of thyroid diseases.  J Clin Endocrinol Metab. 2005;  90 124-127

Correspondence