Dr. Goodyear

In vitro study finds that progesterone metabolites effect expression of estrogen receptors.  The progesterone metabolite 5alphaP increased ER alpha expression.  This is important as ER alpha promotes growth and inflammation.

Study finds that breast cancer cells can produce endogenous progesterone from pregnenolone via 3-beta-hydroxysteroid dehyrdogenase.

Study finds that breast cancer cells can make progesterone endogenously from pregnenolone.  

To be read.

Good discussion of the different effects of progesterone metabolites in breast cancer cell lines (in vitro).  This article focused on the biochemical balance of 5alpha pregnane: 3alpha HP.  The increase in this ration promoted proliferation and metastasis, where a decreased ratio did the opposite

Progesterone metabolites play key role in breast cancer carcinogenesis or inhibition of carcinogenesis.  The key active progesterone metabolites discussed in this article are 5 alpha pregnene and 3 alpha hydroxyprogesterone.

Progesterone metabolites are present on the membrane of ER/PR + as well as ER/PR - breast cancer cell lines.  The balance of 5 alpha pregnane:3 alpha pregnane regulates tumor genesis.  Estradiol increased 5 alpha pregnane receptors as well as 5 alpha pregnane unregulated itself via autocrine activity.  The 3 alpha pregnenes, 3 alpha hydroxyprogesterone and 20 alpha-dihydroprogesterone, decrease the 5 alpha pregnane receptors via paracrine activity.

The receptors for 5 alpha progesterone and 3 alpha hydroxyprogesterone are distinct from other hormone receptors.  These receptors are plasma membrane bound.  Through these receptors, these progesterone metabolites initiate autocrine and paracrine activity.  E2 increased 5 alpha progesterone receptors.  This is very important in ER-/PR- breast cancer, but does still have significance in ER+/PR+ cancer as well.

The progesterone metabolite allopregnanolone is shown to play a significant role in the PMDD symptoms.  The mechanism is via a paradoxical GABA-A effect.

Good review of the physiology of muscle performance during intense exercise.

Little if any proof that creatine causes cramps and dehydration.

Loading dose of creatine, 20 grams/day, over 5-6 days increases total muscle creatine levels.  This has been shown to improve athletic performance.  The phosphocreatine  in Type II muscle fibers are particularly increased.  This can be maintained at 2 grams/day.

Nice review of the data, up to the publication date, on creatine.

Creatine improves swimming performance.  The majority of studies have been on freestyle.

Four day loading dose with 20 grams of creatine significantly improved swimming time in elite swimmers.

Creatine, 15.75 grams daily, increased sprint performance in football players.  The participants of this study were followed for 28 days.

review of the literature at the time found the majority of studies showed positive results with phosphocreatine supplementation.

Creatine loading dose of 25 grams over 4 days shown to increase high-intensity exercise performance in both males/females.

4 days of creatine loading with 25 grams improved times in elite swimmers in 19/22 individuals.  Two months provided no significant benefit.

In this study, creatine + sodium bicarbonate improved time in interval swimming.  All were loaded for 6 days prior to randomization.