TSH suppression requires daily doses of T4 between 2.5 and 2.9 micrograms/kg BW in athyreotic patients and between 1.9 and 2.3 micrograms/kg BW in goitrous patients, with appropriate adjustments in relation to the age of the patient; Assessment of the adequacy of treatment should not be carried out before 6 months after the institution of therapy.

The pattern of estrogen (ER) and progesterone receptors (PR) and their relationship to histo- and cyto-pathological parameters has been studied in 97 cases of benign breast disease and benign phyllode tumors (95 women, of whom 76 were premenopausal, and 2 men). Total (cytosolic + nuclear) ER and PR were assayed by a single-saturating dose method using a tris-KCl buffer. The cut-off between positive and negative ER and PR assay was 100 femtomoles/g tissue. All specimens were processed for histological examination: epithelial and fibroblastic proliferation, epithelial/stromal ratio and presence of focal or diffuse hyalinosis. In 33% of the 46 cases of fibrocystic disease one receptor at least was present (13% ER+, 31% PR+). All the 8 cases in which infiltrating epitheliosis was present were PR+ and 4 of them were also ER+. In 72% of the 31 fibroadenomas one receptor at least was present (19% ER+, 71% PR+). In all these cases levels of receptors were lower than in malignant tumors. An inverse correlation between PR + prevalence and fibrohyalinosis was observed; on the other hand a positive relationship between PR + and fibroblastic (p less than 0.001) or epithelial (p less than 0.01) proliferation was found. In all 5 benign phyllode tumors examined PR + were present at a very high level, almost as high as in malignant tumors. Of the 15 other benign breast lesions, all but one (1 hamartoma) were ER- and PR-.

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The ontogeny of nyctohemeral variations of hypothalamic TRH content was determined in male rats from 7-45 days after birth, exposed to a daily 12-h light, 12-h dark cycle (0600-1800 h light; 1800-0600 h dark) or maintained in complete darkness until 45 days. TRH was extracted from whole hypothalami with 90% methanol and assayed by specific RIA. Hypothalamic TRH extracted from rats at different ages showed immunological, chromatographic, and biological properties identical to those of synthetic TRH. No significant variations in hypothalamic TRH content during the day were observed in 7-, 10-, and 17-day-old rats; a significant change, with a maximal value at 1800 h, was observed in 23-day-old rats, while an adult pattern with a maximal value at 1200 h and a minimal value at 2400 h was found in rats of 31 days of age and became more evident in 45-day-old rats. In animals maintained in complete darkness for 45 days after birth, no significant changes in hypothalamic TRH content at 1200 and 2400 h were observed. These findings indicate that environmental cyclic light-dark exposure is required for the development of diurnal changes in hypothalamic TRH content. Furthermore, any study involving hypothalamic TRH determination should take into account the age of animals and the diurnal variations of TRH.