ABSTRACT
Most patients with acanthosis nigricans have either clinical or subclinical insulin resistance. We undertook a study to estimate the insulin sensitivity of a group of patients referred from the dermatologist with biopsy proven acanthosis nigricans. Thirty-six patients were evaluated in the Endocrinology clinic. Plasma glucose and serum Insulin levels were estimated after a 75 gms oral glucose load (OGTT). An intravenous Insulin Tolerance Test (ITT) was performed with measurement of Glucose Disposal Rate (GDR). There were 28 females and 8 males (M:F--3.5:1; mean age 26.3+/-1.7 years) in the study. 25/36 patients were morbidly obese (BMI--36.0 +/- 1.2 Kg/m2) with an abnormal body fat distribution (WH ratio--0.9 +/ - 0.02). One patient had generalized lipoatrophy. 16/36 patients with acanthosis nigricans had IGT or overt diabetes and all had highly significant hyperinsulinemia (AUCI = 20825 +/ 1287.7 vs. 6340.0 +/- 984.2 mIU/ml/hr in controls, p < 0.0005). The GDR in patients with acanthosis nigricans was reduced (-0.66 +/- 0.07) compared to controls (-0.39 +/- 0.08; p < 0.01). There was a significant positive correlation between indices of adiposity and insulin resistance in subjects with impaired tolerance.
ABSTRACT
AIM: To study the prevalence of insulin resistance (IR) and its sequelae in patients with acanthosis. METHODOLOGY: Thirty six patients (28 females; eight males) with biopsy proven acanthosis nigricans and eight controls were evaluated for insulin sensitivity (IS) by estimating (a) the glucose and insulin responses to a 75 gm glucose load (Oral glucose tolerance test-OGTT), (b) the glucose disposal rate (GDR) during an intravenous insulin tolerance test (ITT). Serum androgen levels (testosterone--Te, androstenedione--ASD, Dehydro-epiandrosterone sulphate--DHEAS) were estimated in the basal state and 60 min after a bolus of insulin. Thyroid function tests (tri-iodo-thyronine--T3, thyroxine--T4, thyroid stimulating hormone--TSH) were performed in all subjects. RESULTS: The acanthotic population, overall had insignificant hyperglycemia (Area under curve of glucose--AUC-G : 17,745.5 +/- 847.5 v/s 11,051.3 +/- 274.5 mg/dl/min) and hyperinsulinemia (Area under curve of insulin -AUC-I: 20,825.2 +/- 1,287.7 v/s 6,340.1 +/- 984.2 microlU/ml/min) compared to controls during OGTT. Eight patients with acanthosis nigricans had impaired glucose tolerance and eight had overt diabetes using WHO criteria. 69.4% of the acanthotic subjects were obese and 13.9% (5/36) were hypertensive. Thyroid dysfunction was present in three (one had hypothyroidism and two had thyrotoxicosis). Reproductive disorders--menstrual irregularity (46.5%), amenorrhea (21.4%), hirsuitism (21.4%) and infertility (3.6%) was encountered in a significant number of acanthotics. Acanthotics overall had statistically higher levels of androgens; Te (females)--0.74 +/- 0.09 v/s 0.27 +/- 0.09 ng/ml (p < 0.005), ASD--1.8 +/- 0.21 v/s 0.94 +/- 0.2 ng/ml (p < 0.005) and DHEAS--1,880.8 +/- 216.3 v/s 772.8 +/- 210.4 ng/ml (p < 0.005). An elevated DHEAS correlated positively to body mass index (BMI) and android obesity. Serum Te levels correlated positively with GDR. Serum insulin levels increased progressively with obesity and acanthosis. Serum insulin was associated with progressive worsening of hyperandrogenism (as seen in non-obese controls, non-obese and obese acanthotics). CONCLUSIONS: Subjects with acanthosis nigricans should be screened for insulin resistance and its clinical and metabolic sequelae. Thyroid dysfunction should be sought in these subjects as it can be easily treated.