Possible Explanation of Nausea
(Copyright 2010, James Michael Howard, Fayetteville, Arkansas, U.S.A.)
This is a possible explanation of nausea in pregnancy that may also explain nausea in general. A number of ideas have to be combined to complete my explanation.
It is my hypothesis that evolution selected DHEA because it optimizes replication and transcription of DNA. Therefore, I think this selection was very important in the evolution of mammals: "Hormones in Mammalian Evolution," Rivista di Biologia / Biology Forum 2001; 94: 177-184.
It is my hypothesis of 1985 that the "fight or flight mechanism" is based on the ratio of DHEA to cortisol. That is, I think DHEA levels determine the amount of motivation an organism brings to a confrontation and cortisol evolved to counteract the effects of DHEA. If cortisol is high enough, then an organism avoids the consequences of a confrontation such as loss of blood, infection, ...death. Evolution would quickly select this mechanism as it would promote future reproduction of more organisms which / who avoid a fight than those who do.
This is also derived from my examination of the adrenal hormone pathways in 1984. It became apparent to me quickly that there really are mainly two pathways of major amounts of hormone production, that is, DHEA and cortisol. (“A Theory of the Control of the Ontogeny and Phylogeny of Homo sapiens by the Interaction of Dehydroepiandrosterone and the Amygdala,” Copyright 1985, James Michael Howard, Fayetteville, Arkansas, U.S.A. (Registered Copyright Txu220580).)
Cortisol has been connected with nausea and, in fact, dexamethasone, which is used to reduce nausea, and reportedly: "an anti-emetic dose of dexamethasone markedly suppresses plasma cortisol..." (Anaesth Intensive Care. 2010 Jul;38(4):667-70). Marijuanna, cannabinoids, have been found to reduce nausea. The reason may be reduction of cortisol. “Hormonal measurements were performed by radioimmunoassay. Basal prolactin (11.5 +/- 4.3 ng/ml) and growth hormone (1.5 +/- 0.7 ng/ml) levels were unchanged after placebo and CBD. In contrast, plasma cortisol levels decreased significantly during the placebo sessions (basal measurement = 11.0 +/- 3.7 micrograms/dl; 120 min after placebo = 7.1 +/- 3.9 micrograms/dl), in agreement with the normal circadian rhythm of this hormone.” (Braz J Med Biol Res 1993; 26: 213-7).
I suggest all tissues rely on optimal levels of DHEA for optimal growth and development and maintenance, thereafter. Therefore, a mother produces DHEA for herself and her fetus until birth, whereupon the fetus stars producing DHEA which stimulates birth. Therefore, the fetus takes DHEA at the expense of the mother. In women of lower DHEA, I suggest this use of DHEA by the fetus increases the mother’s cortisol to DHEA ratio and triggers nausea.
The precursor of DHEA is DHEA sulfate (DHEAS). If DHEAS is high then DHEA is not being produced. As early as 1986, it was found that “In the last trimester, significantly higher DHEA-S concentrations and lower testosterone values were found in women who had suffered from nausea and vomiting in early pregnancy compared to asymptomatic subjects.” (Eur J Obstet Gynecol Reprod Biol1986 Feb;21(2):87-99). Subsequently, it was reported that “Maternal levels of androstenedione and DHEAS associated positively with nausea and vomiting in week 17. In week 33, testosterone and DHEAS associated positively with nausea and vomiting, as well as androstenedione. A calculated emesis score associated positively with increasing average levels of both androstenedione and testosterone during pregnancy, as well as the free testosterone index.” (Acta Obstet Gynecol Scand 2003; 82: 225-8).
Other times of Nausea:
The other phenomena that produce nausea may also be explained by low DHEA or an increased ratio of cortisol to DHEA.