Breast size in relation to endogenous hormone levels, body constitution, and oral contraceptive use in healthy nulligravid women aged 19-25 years.

In 1993 and 1994, the relation between breast size and hormonal factors and body constitution was studied in 65 healthy nulligravid women aged 19-25 years. Twenty-five women were current oral contraceptive users, 20 women were former users, and 20 women had never used oral contraceptives. Breast size was strongly positively correlated with current oral contraceptive use during menstrual cycle days 5-10, as well as days 18-23. No significant effect of former oral contraceptive use was seen on breast size. A significant increase in breast size between cycle days 5-10 and days 18-23 was seen among current oral contraceptive users. Breast size was significantly positively correlated with body mass index (weight (kg)/height (m)2), height, and weight in nonusers (i.e., former and never users combined) but not in current users. In nonusers, during the follicular phase, breast size was significantly positively associated with insulin-like growth factor 1. During the luteal phase, larger breast sizes were significantly associated with higher 17 beta-estradiol and progesterone levels and lower testosterone levels among nonusers. In models for current users, large breast sizes were significantly associated with high prolactin and luteinizing hormone levels and low follicle-stimulating hormone levels during cycle days 5-10. During cycle days 18-23, larger breast sizes correlated with low endogenous progesterone levels.