Progesterone also affects the function of organs such as:

• the cardiovascular system
• the nervous system
• respiratory system;
• the skeletal system.

In reproductive function, progesterone is responsible for:

• facilitating the implantation of the embryo;
• relaxing effect on the uterine muscle;
• contraction of the internal cervical orifice;
• improves blood supply to the uterus.

Progesterone can be given:

• intramuscularly;
• orally;
• vaginally;
• intranasally;
• sublingually;
• rectally.

The first three routes of administration of the hormone are the most common and widely reported in the literature. Current studies show discrepancies between intranasal administration of the hormone and its effect when administered vaginally.

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Oral administration of progesterone is the most convenient form. However, side effects such as nausea, drowsiness and hot flashes may occur. Progesterone is absorbed rapidly.

Intravenous administration requires daily injection to maintain adequate levels of the hormone. Inflammation at the injection site and even abscesses may occur. The hormone is absorbed immediately. A high serum concentration is obtained after 2 hours.