Progesterone can be used by the oral or
rectal route or by intramuscular or subcutaneous injection (
link), while progestins are usually used by the oral route. Levels of progesterone with the oral route have been found using state-of-the-art assays (LC–MS) to be very low (<2 ng/dL at 100 mg/day) and inadequate for satisfactory progestogenic effects ([source](
https://en.wikipedia.org/wiki/Pharmacokinetics_of_progesterone#Oral_administration), [source](/r/MtFHRT/comments/94naq0/oral_progesterone_achieves_very_low_levels_of/)). In accordance, even a high dosage of oral progesterone (400 mg/day) showed no antigonadotropic effect in cisgender men