Estrogen receptors appear undetectable in the C-cells of the human thyroid gland.

An attempt was made to explain the bone-preserving effect of estrogen by analysis of estrogen receptors (OER) in the calcitonin-producing C-cells of the human thyroid gland. Thyroid tissue from twenty patients with benign hyperthyroidism and three patients with medullary thyroid carcinoma was used. The C-cells were identified immunohistochemically using a polyclonal antibody to calcitonin, and by a similar staining technique the adjacent sections were stained for the OER protein using a monoclonal antibody (H 222-ABBOTT, USA). In spite of an intense nuclear staining of the positive control tissue (an OER positive breast carcinoma) no specific OER-staining was identified in C-cells or any other cells of the thyroid gland. Neither a dextran-coated charcoal assay nor a solid-phase immunoenzyme assay revealed any quantitative OER activity in tissue homogenates. Various observations point to a regulating mechanism between calcitonin and estrogen. The nature of this mechanism is not known, but according to our study it is unlikely to be a direct one.