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The authors report on 59 cases of lactation inhibition by different drugs (placebo, etilbestrol, vitamin B6 and bromocriptine). The patients were between 20-30 and did not wish to breastfeed. Relation between basal levels of prolactin (PRLH) and breast turgency, pain, and milk secretion was studied. Examinations were done 24 hours after delivery, and again 7 and 14 days later. There was a significant correlation between basal levels of PRLH and breast turgency at every examination. Pain was related to prolactinemia only 7 and 14 days after delivery, while milk secretion had a significant correlation with prolactinemia 24 hours after delivery, and again 7 days later, but not at the time of the third examination.

The authors review any possible correlation between prolactin and growth hormone in human breast cancer. They find neither a significant relationship between growth hormone and breast cancer nor between prolactin and growth hormone. In many cases however, prolactin levels may be used as a neoplastic marker. The excess of prolactin could originate either in a tumor factor stimulating its secretion by the hypophysis or in an ectopic production of the hormone by tumor tissue.

In a randomized, double-blind study, 12 and 16 mg of metergoline and 5 mg of bromoergocriptine were given daily to three groups of 100 women each for ten consecutive days to prevent lactation. Excellent or good results were obtained in 86%, 90% and 83%, respectively. Serum prolactin (PRL) levels were evaluated in three settings. The first was after a single dose in four groups of patients (4, 6 and 8 mg of metergoline and 2.5 mg of bromoergocriptine were studied for ten hours). Second, for a study of the suckling reflex, PRL levels were measured 15, 30 and 60 minutes after breast stimulation in four groups of five patients each: two groups on the fourth postpartum day with and without metergoline treatment and two groups on the eighth postpartum day (the reflex was suppressed in the two groups treated with metergoline). Third, serum PRL levels rose after the intravenous administration of 200 mg of thyrotropin-releasing hormone (TRH) in another two groups of ten patients, one treated with metergoline and the other not so treated. TRH stimulation was not blocked in the treated groups.

The authors study the nyctohemeral changes of prolactin and growth hormone during the evolution of breast cancer and in fibrocystic mastopathy. Prolactin shows a circadian rhythm with higher amounts during sleep in cancer patients. Changes are not significant for fibrocystic mastopathy, although there is a tendency towards higher concentrations than in the control group. No significant changes were observed for the growth hormone.