What is the normal reference range for p4?

Under normal circumstances, P4 refers to progesterone. The reference ranges are as follows: less than 3.2 nmol/L in males; 2.4–9.4 nmol/L during the ovulatory phase in females; 5.3–86.0 nmol/L in the luteal phase; 64–1280 nmol/L during pregnancy; and 0.3–2.5 nmol/L in the postmenopausal phase. Detailed analysis is as follows:

Progesterone is a steroid hormone primarily produced by the placenta and corpus luteum. The concentration of progesterone in the body is closely related to the growth and regression of the corpus luteum. Progesterone regulates the secretion of certain hormones from the pituitary gland, influences the development and function of reproductive organs, promotes mammary gland development, and causes an increase in basal body temperature. Progesterone testing is mainly used to determine whether ovulation or pregnancy has occurred, assess corpus luteum and placental function, and help diagnose conditions such as threatened miscarriage, luteal phase deficiency, poor placental development, and molar pregnancy. Elevated progesterone levels may result from either pathological or physiological factors. Physiological increases in progesterone typically indicate ovulation, whereas pathological elevations may suggest conditions such as molar pregnancy, adrenal carcinoma, ovarian tumors, or essential hypertension.

Patients who discover elevated progesterone levels should seek timely medical evaluation to rule out underlying diseases and obtain a definitive diagnosis, especially after excluding physiological causes such as ovulation.