🧬 Receptor activity
| Target | Action | Affinity | Source | |
|---|---|---|---|---|
| Progesterone receptor | — | Ki 3.4 nM | CHEMBL | TargetProgesterone receptor Action— AffinityKi 3.4 nM SourceCHEMBL |
| Androgen receptor | — | Ki 8.5 nM | CHEMBL | TargetAndrogen receptor Action— AffinityKi 8.5 nM SourceCHEMBL |
| Fatty acid-binding protein, liver | — | Ki 27 nM | CHEMBL | TargetFatty acid-binding protein, liver Action— AffinityKi 27 nM SourceCHEMBL |
| Glucocorticoid receptor | — | Ki 30.5 nM | CHEMBL | TargetGlucocorticoid receptor Action— AffinityKi 30.5 nM SourceCHEMBL |
| Corticosteroid-binding globulin | — | Ki 41.69 nM | CHEMBL | TargetCorticosteroid-binding globulin Action— AffinityKi 41.69 nM SourceCHEMBL |
| Sigma non-opioid intracellular receptor 1 | — | Ki 260 nM | CHEMBL | TargetSigma non-opioid intracellular receptor 1 Action— AffinityKi 260 nM SourceCHEMBL |
| C-8 sterol isomerase ERG2 | — | Ki 4430 nM | CHEMBL | TargetC-8 sterol isomerase ERG2 Action— AffinityKi 4430 nM SourceCHEMBL |
| Cytochrome P450 2C9 | — | Ki 5500 nM | CHEMBL | TargetCytochrome P450 2C9 Action— AffinityKi 5500 nM SourceCHEMBL |
| Unchecked | — | Ki 6703 nM | CHEMBL | TargetUnchecked Action— AffinityKi 6703 nM SourceCHEMBL |
| Estrogen receptor | — | Ki 10000 nM | CHEMBL | TargetEstrogen receptor Action— AffinityKi 10000 nM SourceCHEMBL |
| Fatty acid-binding protein, intestinal | — | Ki 20000 nM | CHEMBL | TargetFatty acid-binding protein, intestinal Action— AffinityKi 20000 nM SourceCHEMBL |
| Monoclonal antibody (mAb) | — | Ki 36000 nM | CHEMBL | TargetMonoclonal antibody (mAb) Action— AffinityKi 36000 nM SourceCHEMBL |
| 3-beta-hydroxysteroid-Delta(8),Delta(7)-isomerase | — | Ki 100000 nM | CHEMBL | Target3-beta-hydroxysteroid-Delta(8),Delta(7)-isomerase Action— AffinityKi 100000 nM SourceCHEMBL |
Mechanism of action
Progesterone binds and activates its nuclear receptor, _PR_, which plays an important part in the signaling of stimuli that maintain the endometrium during its preparation for pregnancy. Progesterone receptor (PR) is a member of the nuclear/steroid hormone receptor (SHR) family of ligand-dependent transcription factors that is expressed primarily in female reproductive tissue as well as the central nervous system. As a result of its binding its associated steroid hormone, progesterone, the progesterone receptor (PR) modulates the expression of genes that regulate the development, differentiation, and proliferation of target tissues. In humans, PR is found to be highly expressed in the stromal (connective tissue) cells during the secretory phase and during pregnancy. Progesterone may prevent pregnancy by changing the consistency of cervical mucus to be unfavorable for sperm penetration, and by inhibiting follicle-stimulating hormone (FSH), which normally causes ovulation. With perfect use, the first-year failure rate for progestin-only oral contraceptives is approximately 0.5%. The typical failure rate, however, is estimated to be approximately 5%, due to late or missed pills.
Progesterone is a progestinic hormone secreted mainly from the corpus luteum of the ovary during the latter half of the menstrual cycle. Progesterone is formed from steroid precursors in the ovary, testis, adrenal cortex, and placenta. Luteinizing hormone (LH) stimulates the synthesis and secretion of progesterone from the corpus luteum. Progesterone is necessary for nidation (implantation) of the ovum and for maintenance of pregnancy. Although the hormone is secreted mainly during the luteal phase of the menstrual cycle, small amounts of progesterone are also secreted during the follicular phase. High concentrations of the hormone are secreted during the latter part of pregnancy. Amounts comparable to those secreted in women during the follicular phase have been shown to be secreted in males.
Progesterone shares the pharmacologic actions of the progestins. In women with adequate endogenous estrogen, progesterone transforms a proliferative endometrium into a secretory one. The abrupt decline in the secretion of progesterone at the end of the menstrual cycle is principally responsible for the onset of menstruation. Progesterone also stimulates the growth of mammary alveolar tissue and relaxes uterine smooth muscle. Progesterone has minimal estrogenic and androgenic activity.
Progesterone released during the luteal phase of the cycle decreases estrogen driven endometrial proliferation and leads to the development of a secretory endometrium ... . The abrupt decline in the release of progesterone from the corpus luteum at the end of the cycle is the main determinant of the onset of menstruation. If the duration of the luteal phase is artificially lengthened, either by sustaining luteal function or by treatment with progesterone, decidual changes in the endometrial stroma similar to those seen in early pregnancy can be induced. Under normal circumstances, estrogen antecedes and accompanies progesterone in its action upon the endometrium and is essential to the development of the normal menstrual pattern.
Progesterone also increases the ventilatory response of the respiratory centers to carbon dioxide and leads to reduced arterial and alveolar PC02 in the luteal phase of the menstrual cycle and during pregnancy. Progesterone also may have depressant and hypnotic actions in the CNS, which may account for reports of drowsiness after hormone administration.
For more Mechanism of Action (Complete) data for PROGESTERONE (12 total), please visit the HSDB record page.
Pharmacodynamics
Progesterone, depending on concentration and dosage form, and timing of exposure may have several pharmacodynamic effects. These actions, according, to various preparations, are listed below: General effects Progesterone is the main hormone of the corpus luteum and the placenta. It acts on the uterus by changing the proliferative phase to the secretory phase of the endometrium (inner mucous lining of the uterus). This hormone, stimulated by a hormone called _luteinizing hormone_ (LH) is the main hormone during the secretory phase to prepare the corpus luteum and the endometrium for implantation of a fertilized ovum. As the luteal phase concludes, the progesterone hormone sends negative feedback to the anterior pituitary gland in the brain to decrease FSH (follicle stimulating hormone) and LH (luteinizing hormone) levels. This prevents ovulation and maturation of oocytes (immature egg cells). The endometrium then prepares for pregnancy by increasing its vascularity (blood vessels) and stimulating mucous secretion. This process occurs by progesterone stimulating the endometrium to decrease endometrial proliferation, leading to a decreased uterine lining thickness, developing more complex uterine glands, collecting energy in the form of glycogen, and providing more uterine blood vessel surface area suitable for supporting a growing embryo. As opposed to cervical mucous changes observed during the proliferative phase and ovulation, progesterone decreases and thickens the cervical mucus, rendering it less elastic. This change occurs because the fertilization time period has passed, and a specific consistency of mucous amenable to sperm entry is no longer required. **Gelatinized capsules** Progesterone capsules are an oral dosage form of micronized progesterone which, chemically identical to progesterone of ovarian origin. Progesterone capsules have all the properties of endogenous progesterone with induction of a secretory phase endometrium with gestagenic, antiestrogenic, slightly antiandrogenic and anti-aldosterone effects. Progesterone opposes the effects of estrogen on the uterus, and is beneficial in women with unopposed estrogen exposure, which carries an increased risk of malignancy. **Vaginal gel and vaginal insert** The gel preparation mimics the effects of naturally occurring progesterone. In the presence of adequate levels of estrogen, progesterone converts a proliferative endometrium into secretory endometrium. This means that the endometrium changes from a growing and thickening stage into a subsequent preparation stage for pregnancy, which involves further preparatory changes. Progesterone is necessary for the development of decidual tissue (specialized tissue amenable to supporting a possible pregnancy). Progesterone is required to increase endometrial receptivity for the implantation of a fertilized embryo. Once an embryo is implanted, progesterone helps to maintain the pregnancy. **Injection (intramuscular)** Intramuscularly injected progesterone increases serum progesterone and aids in the prevention of endometrial tissue overgrowth due to unopposed estrogen (which leads to abnormal uterine bleeding and sometimes uterine cancer),. In the absence or deficiency of progesterone, the endometrium continually proliferates, eventually outgrowing its limited blood supply, shedding incompletely, and leading to abnormal and/or profuse bleeding as well as malignancy. **Tablets, contraceptive** Progesterone-only contraceptive tablets prevent conception by suppressing ovulation in about half of users, causing a thickening of cervical mucus to inhibit sperm movement, lowering the midcycle LH and FSH hormone peaks, slowing the movement of the ovum through the fallopian tubes, and causing secretory changes in the endometrium as described above.
Pharmacokinetics
Half-life
Absorption half-life is approximately 25-50 hours and an elimination half-life of 5-20 minutes (progesterone gel). Progesterone, administered orally, has a short serum half-life (approximately 5 minutes). It is rapidly metabolized to _17-hydroxyprogesterone_ during its first pass through the liver.
Due to the sustained release properties of Prochieve, progesterone absorption is prolonged with an absorption half-life of approximately 25-50 hours, and an elimination half-life of 5-20 minutes. Therefore, the pharmacokinetics of Prochieve are rate-limited by absorption rather than by elimination.
The elimination half life of progesterone is approximately 5 minutes ...
Progesterone has a short plasma half-life of several minutes.
Absorption
**Oral micronized capsules** Following oral administration of progesterone in the micronized soft-gelatin capsule formulation, peak serum concentration was achieved in the first 3 hours. The absolute bioavailability of micronized progesterone is unknown at this time. In postmenopausal women, serum progesterone concentration increased in a dose-proportional and linear fashion after multiple doses of progesterone capsules, ranging from 100 mg/day to 300 mg/day. **IM administration** After intramuscular (IM) administration of 10 mg of progesterone in oil, the maximum plasma concentrations were achieved in about 8 hours post-injection and plasma concentrations stayed above baseline for approximately 24 hours post-injection. Injections of 10, 25, and 50 mg lead to geometric mean values for maximum plasma concentration (CMAX) of 7, 28, and 50 ng/mL, respectively. Progesterone administered by the intramuscular (IM) route avoids significant first-pass hepatic metabolism. As a result, endometrial tissue concentrations of progesterone achieved with IM administration are higher when compared with oral administration. Despite this, the highest concentrations of progesterone in endometrial tissue are reached with vaginal administration. **Note on oral contraceptive tablet absorption** Serum progestin levels peak about 2 hours after oral administration of progesterone-only contraceptive tablets, followed by rapid distribution and elimination. By 24 hours after drug administration, serum levels remain near the baseline, making efficacy dependent upon strict adherence to the dosing schedule. Large variations in serum progesterone levels occur among individuals. Progestin-only administration leads to lower steady-state serum progestin levels and a shorter elimination half-life than concurrent administration with estrogens.
Progesterone metabolites are excreted mainly by the kidneys. Urinary elimination is observed for 95% of patients in the form of glycuroconjugated metabolites, primarily 3 a, 5 ß–pregnanediol (_pregnandiol_). The glucuronide and sulfate conjugates of pregnanediol and pregnanolone are excreted in the urine and bile. Progesterone metabolites, excreted in the bile, may undergo enterohepatic recycling or may be found excreted in the feces.
When administered vaginally, progesterone is well absorbed by uterine endometrial tissue, and a small percentage is distributed into the systemic circulation. The amount of progesterone in the systemic circulation appears to be of minimal importance, especially when implantation, pregnancy, and live birth outcomes appear similar for intramuscular and vaginal administration of progesterone.
**Apparent clearance** 1367 ± 348 (50mg of progesterone administered by vaginal insert once daily). 106 ± 15 L/h (50mg/mL IM injection once daily).
PROMETRIUM Capsules are an oral dosage form of micronized progesterone which is chemically identical to progesterone of ovarian origin. The oral bioavailability of progesterone is increased through micronization.
After oral administration of progesterone as a micronized soft-gelatin capsule formulation, maximum serum concentrations were attained within 3 hours. The absolute bioavailability of micronized progesterone is not known.
Metabolism
Progesterone is mainly metabolized by the liver. After oral administration, the major plasma metabolites found are 20 a hydroxy-Δ4 a-prenolone and 5 a-dihydroprogesterone. Some progesterone metabolites are found excreted in the bile and these metabolites may be deconjugated and subsequently metabolized in the gut by reduction, dehydroxylation, and epimerization. The major plasma and urinary metabolites are comparable to those found during the physiological progesterone secretion of the corpus luteum.
Progesterone undergoes both biliary and renal elimination. Following an injection of labeled progesterone, 50-60% of the excretion of progesterone metabolites occurs via the kidney; approximately 10% occurs via the bile and feces, the second major excretory pathway.
Progesterone is metabolized primarily by the liver largely to pregnanediols and pregnanolones. Pregnanediols and pregnanolones are conjugated in the liver to glucuronide and sulfate metabolites. Progesterone metabolites which are excreted in the bile may be deconjugated and may be further metabolized in the gut via reduction, dehydroxylation, and epimerization.
The major urinary metabolite of oral progesterone is 5beta-pregnan-3alpha, 20alpha-diol glucuronide which is present in plasma in the conjugated form only. Plasma metabolites also include 5beta-pregnan-3alpha-ol-20-one (5beta-pregnanolone) and 5alpha-pregnan-3alpha-ol-20-one (5beta-pregnanolone).
The hormone is reduced to pregnanediol in the liver and conjugated with glucuronic acid, and then excreted mainly in urine.
For more Metabolism/Metabolites (Complete) data for PROGESTERONE (9 total), please visit the HSDB record page.
Protein binding
96%-99% bound to serum proteins, primarily to serum albumin (50%-54%) and transcortin (43%-48%).
External links
Fact-sheets from PsychonautWiki. Harm-reduction reference only — not medical advice.