The plummeting post-partum and even menopausal estrogenic levels cause thinning and falling hair, sometimes resulting in clinically significant hair loss, the so-called telogen effluvium.
In essence, estrogens help our skin and hair remain youthful.
Future research will hopefully shed some light on the interactions between estrogens and progesterone, to better understand these described changes in skin and hair.
Testosterone is the chief male sex hormone and is the primary reason for everything that makes a man, well… male.
Prolactin is the primary LH in dogs and is required for sustenance of the corpus luteum,which produces progesterone. Prolactin synthesis by the pituitary gland is stimulatedindirectly by serotonin because serotonin inhibits dopamine, which is a direct inhibitorof prolactin. Therefore, increased levels of serotonin will block dopamine's ability toinhibit prolactin and prolactin levels will increase. Around day 25 to 30 of pregnancyafter the LH surge, prolactin levels significantly increase. When drugs that stimulatedopamine (dopamine agonists), such as bromocriptine or cabergoline, are administered tothe pregnant bitch during this prolactin increase, abortion occurs. The major limitationto use of these drugs is that they are less effective and require high dose administrationwhen used prior to day 40 of the pregnancy. Because inducing abortion in the pregnantbitch is not recommended after day 40, high-dose use of dopamine agonists has the effectof producing greater side-effects including vomiting and inappetence.
At one time, large doses of estrogen prior to implantation of the fertilized blastocysts were utilized as a method to prevent pregnancy after mating. Fertilization of the ova takes place in the oviduct, the tube leading from the ovary to the uterus. For approximately 5-10 days after fertilization, the blastocyst will continue developing outside the uterus in the oviduct before the tubo-uterine junction opens allowing the blastocyst to finally migrate to the uterus and implant. When large doses of estrogen are administered to the bitch immediately after breeding, the tubo-uterine junction will remain closed and the blastocysts will degenerate in the oviduct. If given after day 10 of the pregnancy when the embryos have already migrated into the uterus, the estrogen will interfere with the development of the uterine glands, which will prevent the embryos from implanting.
To be effective, prostaglandin treatment must be administered at least 13-15 daysfollowing the LH surge. Because many side-effects are obtained by using naturalprostaglandins, synthetic analogues have been created to imitate the natural moleculewhile reducing the side-effects associated with use. Such side-effects can be severe andinclude excessive salivation, vomiting, diarrhea, loss of coordination, respiratorydistress, anxiety and pupil dilation/constriction. However, even the analogues can causesignificant complications so many veterinarians will combine prostaglandin treatment withparasympatholic agents such as atropine or butylscopolamine to reduce severity of thesymptoms. Despite these approaches, bitches must still be hospitalized for the extent ofthe treatment regimen. Additionally, abortion with prostaglandins is more easily inducedwhen treatment is administered beginning at least 30 days after mating, when implantationof the embryos has already occurred. Lower doses are required to achieve termination ofpregnancy at this point in time, and hence, fewer or less severe side-effects occur.
Side-effects resulting from use of high-dose estrogen are severe and potentially fatal. Bone marrow toxicity with severe hematological side-effects often lead to death. Additionally, the abnormal ratio of estrogen: progesterone induced by high-dose estrogen treatment often leads to cystic hyperplasia of the uterine glands and pyometra, conditions that will preclude future fertility in the bitch. Though orally administered estrogen results in fewer and less severe adverse effects, clinical studies demonstrate that orally administered estrogen is ineffective at inducing pregnancy termination.
For example, a recent study showed that sun-damaged skin does not improve with estrogen treatment.3 Moreover, side effects have even shown increased pigmentation on cheeks after hormonal therapy.2 The research on male skin and hormone therapy is even more scant.
Estrogens include estradiol, the most abundant form in adult females, estriol, the primary estrogen during pregnancy and estrone, which is produced during menopause.
Because effective termination of pregnancy is achieved only when utilizing high-doses of estrogen and because of the serious side-effects associated with this treatment, this method is no longer advocated as a means to end unwanted pregnancy in the bitch.