Brooke Shields' Daughter Reveals Type 1 Diabetes Diagnosis

Brooke Shields' daughter's getting real about her health issues ... admitting she's quietly been dealing with diabetes for years -- beginning when she was just a high schooler.

Rowan Henchy, Brooke's 21-year-old daughter who she shares with director Chris Henchy, spoke with People in an article published Saturday ... and, she says she was diagnosed with the type 1 diabetes when she was in her first year of high school.

Henchy says she knew something was wrong when she lost weight rapidly despite eating twice as much at every meal.

Add that to screwed up eyesight, frequent trips to the bathroom and what she calls a "really bad toe infection" ... and, RH just knew something was totally out of wack.

Rowan says the diabetes and transitioning schools proved to be an issue for her ... 'cause she didn't have many friends, so she had to work through depression all while adjusting to her new normal.

Brooke says she thinks it made Rowan grow up quickly, with constantly needing to check her glucose levels and injecting herself with insulin maturing her quickly.

For her part, Brooke's also shining awareness on the condition ... starring in a coming-of-age film "Quarter" -- focused on a girl living with it.