Study, 1975
Does suppressing prolactin affect how the menstrual cycle works?
No clear difference was found. When prolactin was suppressed to low levels, the menstrual cycle continued with the same pattern of hormonal changes.
What they did
Fifteen women in two groups (8 breastfeeding and 7 with regular periods) took bromocriptine 1 mg three times daily. The breastfeeding group took it for 14 days. The menstruating group took it for a whole cycle, with a cycle measured before treatment. Blood was taken during sleep.
What they found
Prolactin dropped from 10.8 to 3.7 ng/mL in breastfeeding women and from 9.5 to 3.2 ng/mL in menstruating women. This drop was enough to stop milk production within 24 to 48 hours in breastfeeding women. However, the pattern of hormones during the menstrual cycle stayed the same despite the large prolactin drop.
What it means for you
Prolactin does not appear to control how the menstrual cycle works. The main limit is the small sample size and lack of a placebo comparison in the menstruating women.
10.8 to 3.7
prolactin drop in breastfeeding women (ng/mL)
9.5 to 3.2
prolactin drop in menstruating women (ng/mL)
24 to 48 hours
time for milk production to stop
About the study
- Original title
- Lack of action of prolactin suppression on the regulation of the human menstrual cycle
- Authors
- del Pozo E, Goldstein M, Friesen H et al.
- Journal
- American journal of obstetrics and gynecology
- Year
- 1975
- Study design
- Study
- Participants
- 48
- What was tested
- Bromocriptine (a drug that suppresses prolactin) - 1 mg three times daily
- Read the paper
- doi.org/10.1016/0002-9378(75)90494-9
Topics
Related studies
Study, 1979
How do brain waves change after giving birth compared to pregnancy?
Cohort study, 2026
Does having PMS before pregnancy increase the risk of postpartum depression?
Systematic review, 2026
Why do some women experience mood changes linked to their menstrual cycle?
Cohort study, 2026
Do premenstrual disorder and postpartum depression share the same genetic causes?
Cohort study, 2025
Is there a link between premenstrual disorders and autoimmune disease?
Cohort study, 2025
Do women with a history of PMS or PMDD have more depression during pregnancy and after birth?