Orbital accumulation of hydrophilic, interstitial glycosaminoglycans (GAG) and subsequent expansion of retrobulbar tissue lead to the clinical manifestation of exophthalmos in patients with thyroid eye disease (TED). In order to analyze whether the alteration of distribution pattern and biochemical composition of GAG and proteoglycans play a role in the development of the disease, a highly specific high-pressure liquid chromatography (HPLC) method was developed. The concentration of total GAG, chondroitin sulfate A (CA), dermatan sulfate (DS), and hyaluronic acid (HA) was determined in patients and controls, revealing marked differences in urinary concentration of total GAG and HA, as well as an elevation of CA in patients versus controls. Method sensitivity was 0.86 for patients with active disease, and 0.87 for patients with untreated ophthalmopathy, whereas specificity was 1.0 for patients with inactive disease. Patients with increased GAG concentration responded well to steroids and/or orbital irradiation. Furthermore, distribution pattern of orbital extracellular matrix GAG exhibited a significant increase in the tissue fractions of CA and HA in patients with TED in comparison to controls. In conclusion, GAG polysaccharides not only play a major role in the pathogenesis of TED but have been successfully introduced as an activity marker of the disease.

The influence of diabetic nephropathy on urinary glycosaminoglycan distribution was assessed in 96 patients with insulin-dependent diabetes mellitus (IDDM, 49 female, age: 16 - 64 yrs, median 35; duration of IDDM: 0 - 43 yrs, median 13 yrs) in comparison to 103 healthy controls (57 female, 17 - 82 yrs, median 40 yrs). Glycosaminoglycan concentration of 24 h urine samples was determined by means of precipitation with cethylpyridinium chloride and potassium acetate in ethanol followed by a colorimetric test with carbazole. A marked difference (p = 0.0008) in urinary glycosaminoglycan excretion between patients (19.0, 12.4, 35.6 mg/24 h, median, 25th, 75th percentile) and controls (15.8, 10.4, 21.6 mg/24h) could be detected. In patients with insulin-dependent diabetes mellitus of longer duration, glycosaminoglycan excretion was increased (<10 years: 17.3, 10.8, 30.5 mg/24 h; > 10 yrs: 23.3, 16.0, 39.1 mg/24 h; p = 0.03). Furthermore, diabetic patients with manifest nephropathy and retinopathy exhibited a significantly higher glycosaminoglycan excretion compared to patients without nephropathy (40.8, 23.3, 42.2 versus 18.2, 11.4, 31.0 mg/24 h, p = 0.005) or retinopathy (31.9, 16.6, 41.6 versus 17.6, 11.2, 26.7 mg/24 h, p = 0.009). Thus, the results of this study demonstrate a close relationship between diabetic nephropathy and the renal glycosaminoglycan excretion.

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An increased accumulation of glycosaminoglycans (GAG) in the orbita has been reported in endocrine ophthalmopathy (EO). In this study we investigated whether antibodies directed against GAG are present in the sera of 52 EO patients and 47 healthy controls. Three out of 52 patients exhibited low titers of antinuclear antibodies and all patients were negative for antibodies against extractable nuclear antigens. Isotype IgG antibodies were detected by means of an ELISA using hyaluronic acid and dermatan sulfate as antigens. Values were expressed as optical density at 405 nm. In comparison to the control group (0.445, 0.364, 0.588; median, 25th, 75th percentile) significantly (p < 0.001) higher hyaluronic acid antibody levels were found in EO patients (0.626, 0.473, 0.801). Untreated patients had significantly higher hyaluronic acid antibody values compared to controls (0.770 vs 0.437, median, p < 0.005). Thyroid status or antithyroid treatment did not influence binding of hyaluronic acid antibodies. When screening for dermatan sulfate antibodies no such difference could be observed between patients and controls. Thus, the detection of GAG antibodies in EO patients emphasizes the important role of glycosaminoglycans in the pathogenesis of thyroid eye disease.

In this study, similar bioavailability and bioequivalence for levothyroxine and the combination of levothyroxine with iodide were demonstrated.