Cultures of skin fibroblasts show variation of androgen binding with culture conditions; binding variations are usually avoided by using confluent cultures. In this work, we analysed the effect of cell density and mitogenic agents on the level of androgen receptor (AR) of cultured human skin fibroblasts. Results demonstrated that in cultures of human skin fibroblasts, cellular binding of dihydrotestosterone was higher in cells grown at low than at high cell density. The reduction in binding resulted from a decrease in the number of high affinity receptors and not from a change in receptor affinity. Immunocytochemistry for AR showed greater staining intensity in cells grown at low than at high cell density. Additionally, immunoblot analysis demonstrated more AR protein in low cell density cultures. On the other hand, it was observed that cells grown at low cell density showed diminished androgen binding capacity after 24 h of treatment with insulin-like growth factor (IGF-l), basic fibroblast growth factor (bFGF), epidermal growth factor (EGF), or granulocyte-colony stimulating factor (G-CSF); this effect of growth factors was not observed in cells grown at high cell density. In conclusion, we found that cell density of cultures and mitogenic agents can regulate AR binding activity in human fibroblasts. While we do not yet know how changes in cell density affect the amount of AR, we conclude that the mechanism could be mediated by activation of the tyrosine kinase pathway, as the effect was reproduced by mitogens.

Thyroid cancer among children and adolescents Clinical and pathological features of 36 patients with thyroid cancer under 19 years of age were studied: at histological examination 55.5% (20 patients) had papillary carcinoma and 44.5% (16 patients) the follicular type of neoplasm. No cases of undifferentiated and medullary cancers were detected. Twenty two (61%) cases had single nodule goiters, while in 14 (39%) patients these were multinodular. Nine cases of early metastases to regional lymphatic tissues and 4 of distant metastases were seen. All patients underwent surgical treatment and were given replacement therapy with thyroid hormones. Additionally nineteen patients were treated postoperatively with I* 31. There were 4 cases of postoperative hypoparathyroidism, one of inferior laryngeal nerve lesion and one operating room death. Three regional recurrences of thyroid carcinoma were seen. Mean length of follow up was 15.4 (range 1 to 40) years and included all cases: there was only one death attributable to thyroid cancer. The prognosis and evolution of thyroid cancer in children and adolescents looks rather benign even in the presence of regional or long distance metastases.

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