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			Concern Treatment Pregnancy Experiences Pregnancy Maintaining Your Pregnancy Hormonal Support Role of Hormones Hormonal Changes		Hormonal Changes in Pregnancy The placenta is a highly vascular organ that develops over the first weeks of pregnancy to provide the foetus with oxygen, nutrients and other substances. The placenta also produces hormones that are important to maintaining pregnancy. The four major hormones produced by the placenta are hCG, progesterone, oestrogens and human placental lactogen (HPL). Human Chorionic Gonadotropin (hCG) hCG is important in early pregnancy. It serves to maintain the corpus luteum until the placenta is able to assume completely the secretion of progesterone and oestrogens. Progesterone Progesterone aids in the implantation of the embryo, and supports and thickens the endometrium. In addition, progesterone acts to stimulate the development of the breast glands involved in milk production. Progesterone is also thought to play a role in suppressing the maternal immunological response to foetal antigens. Progesterone is produced by the corpus luteum in early pregnancy. By the seventh week of pregnancy, progesterone is being produced by both the corpus luteum and the placenta. By week 12, progesterone secretion is taken over totally by the placenta. At the end of pregnancy, progesterone is thought to play a role in parturition, the process leading up to birth. Female Hormones During Ovulation Oestrogen Oestrogens stimulate uterine growth during pregnancy to support the growing foetus. Oestrogens also serve to stimulate breast growth. During pregnancy, levels of oestrone and oestradiol increase to approximately 100 times normal levels and oestriol levels increase by one thousandfold, as shown in the figure below. Human Placental Lactogen (HPL) HPL is the hormone that serves to stimulate the growth and development of breast tissue in preparation for lactation. It also plays a role in metabolism during pregnancy. Lactation Oxytocin is a hormone that is released from the posterior pituitary. The role of this hormone is not precisely clear, but it is concerned with initiating labour and causing the uterus to contract to its former size. It also plays an important part in inducing the secretion of milk from the breasts during lactation (i.e. it causes the breast to eject milk). The hormone prolactin is released from the anterior pituitary. Prolactin seems to act directly on target tissues without stimulating other glands and, like the gonadotropins, is very much concerned with the controlling reproduction. Prolactin in the female stimulates the breast to produce milk. When it is present in large amounts, it also inhibits ovulation and the menstrual cycle. After delivery, secretion of both of these hormones is stimulated by the action of the baby sucking on the breast. When a baby is first put to the breast, it receives a thick liquid called colostrum, which is particularly rich in proteins, including maternal antibodies that help to protect the newborn baby from infection. True milk does not appear until two or three days after birth. The baby sucking at the breast simulates the production of milk so that the breast adjusts to the baby’s demands; milk production gradually increases as the baby grows and wants more. Menopause The ageing of the ovary results in a gradual failure of response of the follicles to FSH stimulation and the secretion of oestrogen declines. As the level of oestrogen continues to fall, there is less feedback inhibition of the pituitary gland and thus some increase in FSH production occurs towards the end of this phase of life (climacteric).  Around the same time, the mid cycle LH peak is lost and anovulatory menstrual cycle occurs. As ovarian function further declines, ovulation ceases completely. The absence of corpora luteum results in a reduction in progesterone secretion and eventually oestrogen levels become so low that menstrual bleeding becomes irregular and finally ceases. At this point, FSH levels are very high. Because of this FSH was, until recently, extracted from the urine of postmenopausal women to make FSH/hMG preparations used in the treatment of infertility. Menopausal symptoms are related to the falling oestrogen levels and the associated release of pituitary function. The rise in secretion of FSH may be associated with an increase in secretion of some of the other pituitary hormones, including thyroid-stimulating hormone (TSH) and adrenocorticotrophic hormone (ACTH). An increase in TSH in association with the imbalance between oestrogen and gonadotropins often results in hot flushes and excessive sweating due to vasomotor instability. Emotional lability may also be related to the effect of TSH on its target organs. An increase in ATCH chiefly results in an excessive secretion of adrenocortical androgens, which causes hirsutism (particularly noticeable on the face). The failure of oestrogen production, apart from its indirect effects via the pituitary, is reflected primarily on the secondary sex organs. The breasts become smaller and lose their shape, the vulva and vaginal tissues become less vascular and their epithelium more susceptible to injury and infection. Atrophic vaginitis with cracking, soreness and bleeding may occur. The ovary and uterus atrophy, and the endometrium disappears completely. The low oestrogen levels after menopause can also be associated with osteoporosis, with resulting weakness of the weight bearing bones, particularly the vertebrae and the neck of the femur. The majority of the symptoms associated with the menopause may be ameliorated by long-term hormone replacement therapy.
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