Components of biological variation, including seasonality, in blood concentrations of TSH, TT3, FT4, PRL, cortisol and testosterone in healthy volunteers - Maes, M; Mommen, K; Hendrickx, D; Peeters, D; D’Hondt, P; Ranjan, R; De Meyer, F; Scharpe, S (Clin Endocrinol, 1997)