Changes in the Endocrine System during Pregnancy

Subject: Midwifery I (Theory)

Overview

The placenta releases several hormones, the most significant of which are steroid hormones and protein hormones. The protein hormones are human chorionic gonadotropin (HCG), placental lactogen (HPL), chorionic thyrotropin (HCT), chorionic corticotropin (HCC), pregnancy-specific B-1 glycoprotein (PSBG), and pregnancy-associated plasma protein (PAPP). Human chorionic gonadotropin hormone is produced by trophoblast cells from the time the fertilized egg is embedded. HCG excreted from the kidney appears in the urine, particularly in the first week of pregnancy, and serves as the basis for a pregnancy test. Estrogen and Progesterone are steroid hormones.

Placental Hormone

The placenta produces a number of hormones, the most important of which are:

  1. Steroid hormones
    1. Estrogen: oestriol, oestradiol, and oestrone
    2. Progesterone
  2. Protein hormones:
    1. Human chorionic gonadotropin (HCG)
    2. Human placental lactogen (HPL)
    3. Human chorionic thyrotropin (HCT)
    4. Human chorionic corticotropin (HCC)
    5. Pregnancy-specific B-1 glycoprotein (PSBG)
    6. Pregnancy-associated plasma protein (PAPP)

Human Chorionic Gonadotropin Hormone

This is produced by trophoblast cells from the time the fertilized ovum is embedded. For the first three months of pregnancy, this is released into the maternal circulation and encourages the growth of the corpus luteum. As a result, the corpus luteum continues to produce estrogen and progesterone throughout the three months of pregnancy.

The placenta is fully formed and takes over the production of estrogen and progesterone by the 12th and 13th weeks, so HCG production begins to reduce around the 10th week and the corpus luteum gradually declines. HCG released by the kidney appears in the urine, particularly in the first week of pregnancy, and serves as the basis for the pregnancy test.

Estrogen

It is produced by the corpus luteum before the 12th week of pregnancy and after the 12th week of pregnancy. The placenta, in collaboration with the fetus, produces it.

Estrogen encourages growth in the uterus as well as the breast duct system, the nipple, and the vaginal lining. They are also in charge of water and electrolyte retention in bodily tissue, ovulation suppression, and lactation inhibition during pregnancy.

Progesterone

Progesterone induces the development of thick vascular deciduas, which are ready for the implantation of the ovum, and it generally keeps the deciduas healthy throughout the pregnancy. It is in charge of the complete development of the glandular tissue in the breast, preparing it for milk release.

The plain muscle is relaxed by progesterone. The uterus arose to accommodate the growing embryo and placenta without causing uterine contractions. If progesterone production is inadequate, the uterus may initiate rhythmic contractions and abortion may occur.

This calming effect may be observed in various simple muscles across the body. The ureters are impacted and get kinked and diluted, resulting in stagnant urine, which predisposes to urinary tract infection, which is prevalent in pregnancy. Relaxation of the plain muscle in the vein wall may result in the formation of varicose veins in the legs, rectum, and vulva. This impact is exacerbated by the pressure of the growing uterus on the pelvic vein, which slows venous return from the legs even further.

Human Placental Hormone

It functions similarly to the pituitary human growth hormone. It is found in maternal blood during early pregnancy. It is in charge of a fetus's growth and regulates fat metabolism to benefit the fetus, as well as stimulating breast growth and development throughout pregnancy.

Thyroid Hormone

As a result of high estrogen levels and increased iodine excretion, the thyroid gland grows in size, and thyroid-binding globulin (TBG) levels rise. Total T4 levels rise, while free T2 and T4 levels remain unchanged, preserving the euthyroid condition. The decrease in free thyroxin promotes thyroid-stimulating hormone, causing the thyroid to expand. Increased hair loss, which is common during pregnancy, can be a sign of a changed thyroid hormone.

  1. Pregnancy
  2. Increased plasma binding protein
  3. Increased bound form thyroxine
  4. Decreased free toxin levels

During pregnancy, the basal metabolic rate rose by as much as 20-25 percent, most likely due to oxygen conjunction by the fetus.

Pituitary Gland

During pregnancy, the anterior pituitary gland expands as well. During pregnancy, there is an increase in ACTH, thyrotrophic hormone, and melanocyte stimulating hormone, which causes an increase in skin pigmentation. The increased levels of estrogen and progesterone hormone decrease luteinizing hormone and follicle-stimulating hormone.

The posterior pituitary gland is stimulated to create more and more oxytocin.

Adrenal Gland

During pregnancy, the size and activity of the gland increase, particularly corticosteroid production, for example. Mineralocorticoids, glucocorticoids, and sex steroids are all examples of steroid hormones.

Pancreas

The increased metabolic needs of the mother and fetus produce a need for fuel, resulting in a state of accelerated famine. Fasting hypoglycemia and starving ketosis are both prevalent.

To treat symptomatic hypoglycemia, pregnant women should eat small, frequent meals.

Insulin resistance increases as pregnancy progresses, owing to insulin antagonism by human placental lactogen.

References

  • Kovacs CS. Calcium metabolism during pregnancy and lactation. NCBI Bookshelf. http://www.ncbi.nlm.nih.gov/books/NBK279173/
  • HealthLine. 2005. 2017 http://www.healthline.com/health/pregnancy/bodily-changes-during
  • BC Open Textbook. https://opentextbc.ca/anatomyandphysiology/chapter/28-4-maternal-changes-during-pregnancy-labor-and-birth/
  • Hadassah Medical Center. http://www.hadassah-med.com/giving-birth/hadassah-birthing-club/throughout-pregnancy/physiological-changes-during-pregnancy
  • Tuitui R. 2002, A textbook of Midwifery A (Antenatal), 3rd edition, Vidyarthi Pustak Bhandari (Publisher and Distributor), Bhotahity, Kathmandu
  • Tuitui R. 2002, A textbook of Midwifery B (Intranasal), 3rd edition, Vidyarthi Pustak Bhandari (Publisher and Distributor), Bhotahity, Kathmandu
Things to remember
  • The placenta produces a number of hormones, the most important of which are steroid hormones and protein hormones.
  • The protein hormones include human chorionic gonadotropin (HCG), human placental lactogen (HPL), human chorionic thyrotropin (HCT), and human chorionic corticotropin (HCC), pregnancy-specific B-1 glycoprotein (PSBG), and pregnancy-associated plasma protein (PAPP).
  • Human chorionic gonadotropin hormone is produced by trophoblast cells from the time the fertilized ovum is embedded.
  • For the first three months of pregnancy, this is released into the maternal circulation and encourages the growth of the corpus luteum.
  • HCG released by the kidney appears in the urine, particularly in the first week of pregnancy, and serves as the basis for the pregnancy test.
  • Estrogen and progesterone are steroid hormones.
  • Estrogen encourages growth in the uterus as well as the breast duct system, the nipple, and the vaginal lining.
  • Progesterone induces the development of thick vascular deciduas, which are ready for the implantation of the ovum, and it generally keeps the deciduas healthy throughout the pregnancy.
Questions and Answers

Changes in the Endocrine System

Placental Hormone

Numerous hormones are produced by the placenta, however some of the most important ones are:

  • Steroid Hormones
    • Oestrogen, which includes oestriol, oestradial, and oestrone
    • Progesterone
  • Protein Hormones
    • Chorionic gonadotropin from humans (HCG)
    • Placental lactogen in humans (HPL)
    • Chorionic thyrotropin in humans (HCT)
    • Chorionic corticotropin in humans (HCC)
    • Specific to pregnancy B-1 glycoprotein
    • Plasma protein associated with pregnancy

Human Chorionic Gonadotropin Hormone

  • Since the fertilized ovum was embedded, trophoblast cells have been producing this. For the first three months of pregnancy, this is released into the mother's blood, where it encourages the development of the corpus luteum. Therefore, throughout the entire three months of pregnancy, the corpus luteum continues to produce the hormones progesterone and estrogen.
  • The production of estrogen and progesterone is completely taken over by the placenta by weeks 12 and 13, so around week 10 the production of HCG starts to fall and the corpus luteum gradually shrinks. Pregnancy tests are based on the presence of HCG, which is excreted via the kidney, in urine, particularly in the first week of pregnancy.

Estrogen

  • It is produced by the corpus luteum both before and after the 12th week of pregnancy. Together with the fetus, the placenta produces it.
  • In addition to the uterus, estrogen also stimulates growth in the breast duct system, the nipple, and the vaginal lining. They are also in charge of ovulation suppression, water and electrolyte retention in body tissue, and lactation inhibition in pregnancy.

Progesterone

  • Progesterone encourages the growth of dense, vascular deciduas that are prepared for the imbedding of the ovum, and it typically keeps the deciduas healthy throughout the pregnancy. It is in charge of causing the glandular tissue in the breast to fully mature and get ready to secrete milk.
  • Plain muscle is relaxed by progesterone. As a result, the uterus expanded to provide room for the placenta and growing fetus without inducing uterine contractions. A progesterone deficiency may cause the uterus to start contracting rhythmically, which may lead to abortion.
  • Other body simple muscles may experience this calming effect. The ureters are impacted, kinking, and diluted, which causes static in the urine and predisposes to urinary tract infections, which are common during pregnancy. Varicose veins in the legs, rectum, and vulva may develop as a result of the wall of the vein's plain muscle relaxing. The uterus' growing size puts pressure on the pelvic vein, which worsens this effect by delaying the venous return from the legs.

Human Placental Hormone

It resembles the human growth hormone produced by the pituitary. In the early stages of pregnancy, it can be found in the mother's blood. It is in charge of a fetus' growth, modifies the metabolism of fat for the benefit of the fetus, and also promotes breast growth and development during pregnancy.

Thyroid Hormone

Due to high estrogen levels and increased iodine excretion, the thyroid gland enlarges and thyroid binding globulin (TBG) levels rise. Total t4 levels increase, while free T2 and T4 levels remain unaltered, maintaining the euthyroid condition. The thyroid enlarges as a result of the thyroid stimulating hormone being stimulated by the reduced level of free thyroxin. Increased hair loss, a common pregnant symptom, mimics changed thyroid hormone.

  • Pregnancy
  • Plasma binding protein has increased
  • Increased thyroxine in its bound form
  • Lower levels of free toxins

Pregnancy raised the basal metabolic rate by up to 20–25%, most likely as a result of the fetus's use of oxygen.

Pituitary Gland

  • Pregnancy also causes the anterior pituitary gland to expand. During pregnancy, there is an increase in ACTH, thyrotrophic hormone, and melanocyte stimulating hormone, which results in darker skin. The increased levels of estrogen and progesterone hormone repress luteinizing hormone and follicle-stimulating hormone.
  • A greater amount of oxytocin is produced by the posterior pituitary gland as a result of stimulation.

Adrenal Gland

  • The size and activity of the gland do increase slightly during pregnancy, particularly the production of corticosteroids, for example. Glucocorticoids, sex steroids, and mineralocorticoids.

Pancreas

  • The increased metabolic demands of the mother and fetus lead to a demand for fuel and an accelerated famine state. Starvation ketosis and exaggerated fasting hypoglycemia are frequent.
  • The pregnant woman is advised to eat modest, frequent meals in order to combat symptomatic hypoglycemia.
  • Due mostly to insulin antagonistic effects of human placental lactogen, insulin resistance increases as pregnancy progresses.

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