Estimation of truncal adiposity using waist circumference or the sum of trunk skinfolds: a pilot study for insulin resistance screening in hirsute patients with or without polycystic ovary syndrome
Introduction
Obesity, a major public health concern, is a chronic disorder that results from the interaction of numerous social, physiologic, metabolic, and cellular factors [1]. This multifactorial illness is a risk factor for type 2 diabetes mellitus, cardiovascular disease, osteoarthritis, several types of cancer, and certain reproductive and metabolic disorders. It is generally accepted that this risk relates more to the central distribution of fat than to the total amount of body fat [2], [3], [4]. Abdominal obesity is thought to play an important role in insulin resistance (IR) because the increased production of free fatty acids may interfere with the action of insulin [5].
There is strong epidemiologic and clinical evidence [2], [6], [7] that sex steroid hormones greatly influence the regulation of adipose tissue distribution. Androgens may also affect central obesity in women during their reproductive years. The hyperandrogenism that is often seen in patients with polycystic ovary syndrome (PCOS) is associated with obesity of the abdominal phenotype [8], [9], [10], [11]. Hirsutism (excessive hair growth in women in places in which terminal hair is normally not found), one of the major symptoms of PCOS, may result from an overproduction of androgens by the ovaries and/or adrenal glands or by increased sensitivity of the pilosebaceous unit to normal levels of circulating androgens [8], [12], [13]. Thus, overweight and obese hirsute patients with normal or increased androgen levels may serve as a reliable model to assess the relationship of androgens and IR with central adiposity.
Measuring body fat is still a challenge for researchers and clinicians. Fat depots are mainly subcutaneous and intra-abdominal; however, considerable amounts of fat can also reside among and inside muscles, particularly in the elderly [14]. Because fat is widespread and inaccessible, it is not possible to directly and accurately measure whole-body adiposity. Measurement of the waist-hip ratio (WHR) has been shown to reflect the amount of abdominal fat and is widely used to investigate the relations between abdominal fat and metabolic profile [15]. More recently, waist circumference alone has been reported to be more closely correlated with the amount of abdominal fat than with WHR in men and women [16], [17], [18]. Finally, the body mass index (BMI) is the main tool to evaluate total body adiposity. However, studies have shown that a large amount of visceral fat may represent a cardiovascular risk factor even within normal BMI values [5], [18]. Actually, it seems to be better to consider the combined BMI and waist circumference for estimating cardiovascular risk [19].
Currently, the most accurate in vivo method of measuring abdominal adipose tissue is computed tomography (CT). Although CT represents a technological advance and is used as a reference standard, its application in routine clinical practice and research is limited by cost, availability of equipment, and exposure to significant amounts of ionizing radiation [20]. Other techniques that are comparable to CT in terms of accuracy include magnetic resonance imaging [16] and dual-energy x-ray absorptiometry (DXA), a simple method that exposes subjects to minimal amounts of radiation [16], [20]. In addition, one of the simplest methods to evaluate total body fat is the measurement of skinfold thickness [21]. However, there is a dearth of studies evaluating the use of specific skinfolds to determine truncal obesity [22], [23]. Therefore, the aims of the present study were (1) to investigate the influence of androgens on IR and central obesity in overweight or obese hirsute women with or without PCOS and (2) to test the reliability of the sum of trunk skinfolds (subscapular, suprailiac, and abdominal) to estimate truncal adiposity.
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Patients
The study population included women consulting for hirsutism at the Gynecological Endocrinology Unit at Hospital de Clínicas de Porto Alegre, Brazil. Late-onset (nonclassical) congenital adrenal hyperplasia, Cushing syndrome, and androgen-secreting tumors were excluded by appropriate tests as previously described [8], [24], [25]. Patients with diabetes mellitus and hyperprolactinemia (serum prolactin concentrations >20 μg/L on 2 different occasions) were also excluded.
Thirty-seven hirsute
Results
The clinical and anthropometric characteristics of hirsute patients with PCOS or IH are summarized in Table 1. The 2 groups were similar in terms of age, severity of hirsutism, and blood pressure, but WHR was higher in the group with PCOS. Patients with IR constituted 67% of the PCOS group and 30% of the group with IH. Ten patients had impaired glucose tolerance (7 in the group with PCOS and 3 in the group with IH).
Table 2 shows hormonal and metabolic data of hirsute patients. As expected, the
Discussion
In the present study, hirsute patients with PCOS had a higher percentage of truncal adiposity, greater testosterone levels, and free androgen index than women of similar age and degree of hirsutism without PCOS. Moreover, a positive correlation was found between HOMA index and androgens, independent of central adiposity, indicating that hyperandrogenism in PCOS may be additive to elevated waist circumference in increasing risk of IR and seems to be an independent predictor of IR. These findings
Acknowledgment
This study was supported by grants from Conselho Nacional de Desenvolvimento Científico e Tecnológico and PRONEX 26/98 (Programa de Apoio aos Núcleos de Excelência em Pesquisa).
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2015, GeneCitation Excerpt :The exclusion criteria were pregnancy, liver disease, or kidney disease. Anthropometric measurements included body mass index (BMI) (current weight in kg divided by the height in m squared) and waist circumference (measured at the midpoint between the lower rib margin and the iliac crest) (Toscani et al., 2007). Blood pressure was measured after a 10-minute rest, with the patient seated, with both feet on the floor, and the arm supported at heart level.