P. De Nayer

Bone density and markers of bone remodeling in type 1 male diabetic patients

AIMS To assess the prevalence and severity of bone disease in type 1 diabetic patients and to determine serum markers of bone remodeling as well as their relationship with bone mineral density (BMD). METHODS BMD [by dual energy x-ray absorptiometry (DXA)] and serum markers of bone remodeling [osteocalcin, c-terminal telopeptide of type I collagen (CTX)], leptin and osteoprotegerin (OPG) were measured in 42 adult males with type 1 diabetes. Twenty-four non-diabetic subjects served as controls. RESULTS In 40% of the patients, osteopenia at the lumbar spine (L1-L4) and/or at the left hip was found, and 7% met criteria for osteoporosis. L1-L4 BMD z-score was correlated with age (r=0.365, P=0.018) and a similar trend was observed at left hip. L1-L4 BMD z-score was negatively correlated with CTX and osteocalcin (r=-0.343, P=0.028; r=-0.376, P=0.024, respectively). A significant correlation was evidenced between BMD z-score at both lumbar spine and left hip and leptin values (r=0.343, P=0.03; r=0.395, P=0.012, respectively) but after adjustment for weight this correlation was no longer significant. Osteocalcin, CTX and leptin concentrations were comparable between patients and controls, while OPG concentrations tend to be higher in diabetic subjects (P=0.08). CTX was negatively correlated with age (r=-0.390, P=0.012) and positively correlated with osteocalcin (r=0.696, P<0.001). OPG was positively correlated with age (r=0.507, P=0.001). CONCLUSION Our results suggest that in diabetic subjects osteopenia is a relatively frequent complication but bone loss is attenuated with age progression. Whether this is also mediated by OPG and/or leptin remains to be confirmed.

Thyroglobulin synthesis in a thyroid polyribosomal cell-free system

Thyroglobulin (Tg), the major protein of the thyroid gland, has a molecular weight of 660.000 and a sedimentation coefficient close to 19 S (Edelhoch 1965). It contains 8,5% carbohydrate, under the form of 23 oligosaccharides of 2 types: a small unit containing only mannose and N-acetylglucosamine, and a larger unit, with a complex structure, containing in addition sialic acid, fucose and galactose (Cheftel et al. 1964, Spiro 1965). Thyroid polyribosomal cell-free systems have been used by several authors in an attempt to dissociate the steps leading to the completion of the Tg molecule (Cartouzou et al., 1967; Nunez et al., 1967; Morais and Goldberg, 1967; Soffer 1967; Kondo et al., 1967, 1968a, 1968b). Conflicting results were reported. Although such systems can synthesize protein fragments immunochemically related to thyroglobulin, all but one group came to the conclusion that additional factors, related to the membrane components of the cell, are required for the completion of the molecule (Nunez et al., 1967) This report presents evidence for the synthesis of 19 S Tg in a polyribosomal cell free system, and suggests as explanation a mechanism based on an exchange between newly synthesized subunits and subunits of the native Tg molecule.

Intense 18-fluorodeoxyglucose uptake by the thymus on PET scan does not necessarily herald recurrence of thyroid carcinoma.

This is the first report of intense fluorodeoxyglucose positron emission tomography (FDGPET) uptake secondary to thymic hyperplasia during follow-up for thyroid carcinoma. A 36-yr-old woman underwent thyroidectomy for a papillary carcinoma measuring 4 cm in diameter. After two doses of radioiodine, thyroglobulin (Tg) remained detectable following recombinant human TSH (rhTSH) stimulation. A whole body scan (WBS) was negative. On computed tomography (CT) scan, a slightly lobulated thymus was visualized. PET scan showed intense thymic uptake. Following resection, anatomo-pathological analysis showed homogenous hyperplastic thymic gland without neoplastic cells. Two months later, under levothyroxin (L-T4) substitution, Tg was no longer detectable and PET scanning did not show any 18-FDG uptake. This observation suggests that thymic FDG uptake does not necessarily herald recurrence of thyroid carcinoma and must be interpreted with caution in such a setting. Other conditions associated with abnormal uptake by hyperplastic thymus must also be envisaged.