A study of insulin resistance in subjects with acanthosis nigricans.

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.