. 2012 Dec 13;34(2):171–208. doi: 10.1210/er.2012-1008

Table 4.

RBAs and hormonal activities of progestogens via the PR, AR, GR, and MR

Progestogen	PR RBA (%)	AR			GR		MR
Progestogen	PR RBA (%)	RBA (%)	Androgenic activity	Antiandrogenic activity	RBA (%)	Glucocorticoid activity	RBA (%)	Antimineralocorticoid activity
Progesterone	50^a	0^a	?	(+)	10^a	?	100^a	+
	100^b	3^b			11^b		100^b
		1^c			2^c		9^c
Chlormadinone acetate	67^a	5^a	+	—	8^a	+	0^a	—
Cyproterone acetate	90^a	6^a	+	—	6^a	+	8^a	—
Dienogest	5^a	10^a	—	+	1^a	—	0	—
Drospirenone	35^a	65^a	—	+	6^a	—	230^a	+
	19^b	2^b			3^b		500^b
Gestodene	90^a	85^a	?	—	27^a	?	290^a	?
	864^b	71^b			38^b		97^b
Levonorgestrel	150^a	45^a	+	—	1^a	—	75^a	?
	323^b	58^b			7.5^b		17^b
MPA	115^a	5^a	?	—	29^a	+	160^a	—
	298^b	36^b			58^b		3.1^b
		2^c			39^c		0.08^c
Nestorone	136^a	0^a	—	—	38^a	—	ND	ND
Nomegestrol acetate	125^a	42^a	—	+	6^a	—	0^a	—
Norethindrone	75^a	15^a	+	—	0^a	—	0^a	—
	134^b	55^b			1.4^b		2.7^b
Norethindrone acetate	ND	1.7^c	+	—	1.6^c	—	0.07^c	—
Promegestone	100^a	0^a	—	—	5^a	+	53^a	—
Trimegesterone	330^a	1^a	—	?	9^a	—	120^a	?
	588^b	2.4^b			13^b		42^b

RBAs were determined by competitive binding assays using a radiolabeled reference ligand and increasing concentrations of unlabeled competitor ligand and are based on IC₅₀ values in most cases (a and b), whereas K_i (equilibrium dissociation constant for an unlabelled competitor or inhibitor ligand competing for binding of the radiolabeled reference ligand to the receptor) values were determined by homologous and heterologous displacement and using the Cheng-Prusoff equation (c) (73). There is no evidence of significant direct binding for any of these steroids to the ER (RBAs all 0 to <1% relative to estradiol) (7, 41). Hormonal activities are based on animal experiments and taken from Refs. 7 and 41. All the steroids are progestogenic, and all exhibit antiestrogenic activity in animal models via a mechanism independent of the progestin binding to ER. None of them, except norethindrone, exhibits estrogenic activity (7). Key to activity levels: +, effective; (+), weakly effective; —, not effective; ?, literature inconsistent. ND, Not determined.

Values were compiled by cross-comparisons from several competitive binding studies that used different methods and were taken from Ref. 7. Most of the data are from animal tissues or cell lines expressing several receptors, and hence, some are likely to be inaccurate. The reference radiolabeled ligands (100% RBA) were as follows: PR, promegestone; AR, metribolone or R1881; GR, dexamethasone; MR, aldosterone.

Values were determined using recombinant human receptor binding in vitro (74). The reference radiolabeled ligands (100% RBA) were as follows: PR, progesterone; AR, testosterone; GR, dexamethasone; MR, aldosterone.

RBAs were calculated from K_i (equilibrium dissociation constant for an unlabelled competitor or inhibitor ligand competing for binding of the radiolabeled reference ligand to the receptor) values, determined by expressing the human recombinant GR in the A549 cell line (73) or the human recombinant AR or MR (314) in the COS-1 cell line, both deficient in steroid receptors, using the methods outlined in Ref. 73. The reference ligands (100% RBA) were as follows: AR, mibolerone; GR, dexamethasone; MR, aldosterone. Note that for the AR, the RBA for DHT in this assay was 1.3%.