“…For example, (a) plasma prolactin levels in breast cancer patients or in populations exposed to high risk of the disease are not conspicuously higher than those in control subjects (Boyns, Cole, Griffiths, Roberts, Buchan, Wilson & Forrest, 1973;Kwa, de Jong-Bakker, Engelsman & Cleton, 1974;Sheth, Ranadive, Suraiya & Sheth, 1975;Hill, Wynder, Kumar, Helman, Rona & Kuno, 1976;Kwa, Cleton, de Jong-Bakker, Bulbrook, Hayward & Wang, 1976), (b) about 86% of patients with idiopathic galactorrhoea have normal plasma prolactin levels (Kleinberg, Noel & Frantz, 1977) and (c) there is little correlation between milk yield and serum prolactin in cows (Koprowski & Tucker, 1973). The rat seems to be an apparent exception in that a positive correlation between plasma prolactin and the rate of tumour induction by a carcinogen has been demonstrated Hawkins, Drewitt, Freedman, Killin, Jenner & Cameron, 1976). Even in the rat, however, serious discrepancies between bioassay and RIA measurements of prolactin exist (see Nicoli, 1975 for review).…”