Table 1.

Relative ER affinity and abundance of tamoxifen metabolites.

Metabolite	Relative ER Affinity	Relative Abundance
Tamoxifen	1	1
Tam-NoX	n.d	0.07
3OHtam	10	<0.01
Norendoxifen	n.d
α-OHtam	n.d	<0.01
NDtam	0.85	1.78–2.01
NNDDtam	0.46	0.29–0.22
3OHNDtam	n.d	<0.01
4OHtam Isoforms
Z-4OHtam	100	0.01–0.02
Z-4′-Ohtam	10	0.02–0.03
E-4OHtam	<0.03	<0.01
Endoxifen Isoforms
Z-endoxifen	100	0.07–0.09
Z-4′-endoxifen	10	0.05–0.08
E-endoxifen	<0.03	<0.01

Affinity and abundance are relative to tamoxifen. Data on ER affinity was obtained from [31,32,34,37,38]. Information on abundance was extracted from studies using highly specific and selective LC-MS/MS assays [28,39]. n.d = not determined.