Now IMO, selective estrogen receptor modulators(SERMs) such as Clomiphine and Tamoxifen are selective to which tissues they bind too. Clomid being selective to the suprapituitary, while Tamox is selective to breast, bone, and liver ERs. I've come to this conclusion based on the comparison of studies on both SERMs. In every study showing benefit to HPTA from tamoxifin, the duration of the administration is 3-12months(This includes studies cited by William Llewellyn in his Nolva vs Clomid article). In studies showing levels of LH, FSH, and Testosterone checked after short durations of tamox, they were either insignificant, or their was an actual drop. I believe this is because tamox selectively works at the mammery(as well as bone and liver), thus taking longer for LH stimulation to occur.
With clomid, benefit to gonadotrophin concentrations, LH, FSH, and serum testosterone can be seen in short periods of 2-6wks. Because of the apparent selective nature of the two, and given our usual PCT duration, clomid is by far superior at LH stimulation than Nolva. Now both is the wise choice for a couple of reasons:
1. Nolva acts as the preventive measure to the estrogen flux
occured PC while clomid is the primary LH stimulator(Even more so in the case an AI is not used).
2. If your running a longer PCT, clomid needs to be discontinued after a while as it has been shown to desensitize GnRH, this due, IMO, to it's selective nature to the suprapituitary. In the longer forms of PCT, the clomid will be phased out, leaving Nolva and L-dex