My endometrial thickness 1.9cm at age of 24.is this normal?

Varies: The endometrial thickness varies during the menstrual cycle. It is thin after shedding during menses and then thickens throughout the month. We don't usually look at thickness routinely in premenopausal women as the level does not provide useful information in most cases.

19mm is abnormal: 19mm is a thickened endometrium for a menstruating woman. There may be a reason like current pregnancy, polyps, or simply endometrial hyperplasia from too much estrogen without enough progesterone. It occurs in patients with irregular periods for reasons such as PCOS or thyroid disease. http://www.acog.org/Patients/FAQs/Endometrial-Hyperplasia

Your endometrium: Changes thickness throughout your cycle. 1.9 cm is fine for a woman nearing menstruation. Hope this helps!