Pregnancy and Lactation

Describe the hormonal changes that accompany pregnancy and parturition. Outline the processes involved in lactation

Fertilization of the ovum

Implantation At the time of implantation, which occurs about 5-7 days after fertilization, the development is at the blastocyst stage. The trophoblastic cells of the fetus now begin to secrete a peptide hormone, human chorionic gonadotropin (hCG). Fetal hCG possesses a β subunit similar to that of LH, and therefore it has considerable LH activity. The presence of hCG in the urine can be detected by a variety of test kits for the detection of pregnancy

Nutrition of the fetus

Hormonal Maintenance of the Uterine Endometrium

Third month to term Progesterone secretion of the placenta is limited only by the amount of precursor (cholesterol) delivered by low-density lipoproteins (LDL) to the placenta. Estrogen secretion during pregnancy involves a transfer of steroids from the fetal adrenal cortex and fetal liver to the placenta and then to the maternal circulation. Rising serum or urinary estriol is considered an excellent index of both placental function and fetal well-being.

Additional hormones Increased prolactin secretion by the pituitary in response to elevated estrogens Secretion of human chorionic somatomammotropin (hCS):-homology with growth hormone Relaxin

Functions of placenta

Functions of the Placenta

Functions of the Placenta ( contd.)

Functions of the Placenta ( contd.)

Peripheral Effects of Hormonal Changes Massive growth of the uterus, especially the myometrium Increased growth of all components (glands, stroma, and fat) of the breasts

Maternal Compensatory Changes of Pregnancy Estrogen increases renin secretion, and overall increased activity of the reninangiotensin- aldosterone system causes fluid retention and hemodilution. Cardiac output increases but TPR decreases and as a result there is no hypertension. GFR increases and renal threshold decreases. Combined with the increased plasma glucose, glucose often appears in the urine. Increase in levels of thyroxine, adrenocortical hormones, and the sex hormones, basal metabolic rate increases

Parturition Increased Ratio of Estrogens to Progesterone Hormonal Factors That Increase Uterine Contractility Mechanical Factors That Increase Uterine Contractility Increased Ratio of Estrogens to Progesterone Effect of Oxytocin on the Uterus Effect of Fetal Hormones on the Uterus. Stretch of the Uterine Musculature. Stretch or Irritation of the Cervix.

Lactation Growth of the Ductal System—Role of the Estrogens. Development of the Lobule-Alveolar System—Role of Progesterone. Initiation of Lactation—Function of Prolactin

Lactation Estrogens and progesterone stimulate the growth and development of the breasts throughout pregnancy. Prolactin levels increase steadily during pregnancy because estrogen stimulates prolactin secretion from the anterior pituitary. Lactation does not occur during pregnancy because estrogen and progesterone block the action of prolactin on the breast. After parturition, estrogen and progesterone levels decrease abruptly and lactation occurs. Lactation is maintained by suckling, which stimulates both oxytocin and prolactin secretion.

the sudden loss of both estrogen and progesterone secretion from the placenta allows the lactogenic effect of prolactin from the mother’s pituitary gland to assume its natural milk promoting role. Growth hormone, cortisol, parathyroid hormone, and insulin aid milk secretion.

milk-ejection reflex

Ovulation is suppressed as long as lactation continues because prolactin has the following effects: a. Inhibits hypothalamic GnRH secretion. b. Inhibits the action of GnRH on the anterior pituitary, and consequently inhibits LH and FSH secretion. c. Antagonizes the actions of LH and FSH on the ovaries.

The hormone primarily responsible for development of ovarian follicles prior to ovulation is a. Chorionic gonadotropin b. Estradiol c. Follicle-stimulating hormone d. Luteinizing hormone e. Progesterone

Ovulation is caused by a sudden increase in the secretion of a. Estrogen b. Progesterone c. LH d. FSH e. Prolactin

An indication that ovulation has taken place is a An indication that ovulation has taken place is a. An increase in serum FSH levels b. A drop in body temperature c. An increase in serum LH levels d. An increase in serum progesterone levels e. An increase in serum estrogen levels

The normal pattern of progesterone secretion during the menstrual cycle is exhibited by which of the curves shown below?

In the following graph of changes in endometrial thickness during a normal 28-day menstrual cycle, the event designated “A” corresponds most closely to a. The menstrual phase b. The maturation of the corpus luteum c. The early proliferative phase d. The secretory phase e. Ovulation

The increase shown at point A is caused by the effect of (A) estrogen on the anterior pituitary (B) progesterone on the hypothalamus (C) follicle-stimulating hormone (FSH) on the ovary (D) luteinizing hormone (LH) on the anterior pituitary (E) prolactin on the ovary

The source of the increase in concentration indicated at point C is the (A) hypothalamus (B) anterior pituitary (C) corpus luteum (D) ovary (E) adrenal cortex

The source of the increase in concentration at point D is the (A) ovary (B) adrenal cortex (C) corpus luteum (D) hypothalamus (E) anterior pituitary

A 38-year-old man who has galactorrhea is found to have a prolactinoma A 38-year-old man who has galactorrhea is found to have a prolactinoma. His physician treats him with bromocriptine, which eliminates the galactorrhea. The basis for the therapeutic action of bromocriptine is that it (A) antagonizes the action of prolactin on the breast (B) enhances the action of prolactin on the breast (C) inhibits prolactin release from the anterior pituitary (D) inhibits prolactin release from the hypothalamus (E) enhances the action of dopamine on the anterior pituitary

Which of the following explains the suppression of lactation during pregnancy? (A) Blood prolactin levels are too low for milk production to occur (B) Human placental lactogen levels are too low for milk production to occur (C) The fetal adrenal gland does not produce sufficient estriol (D) Blood levels of estrogen and progesterone are high (E) The maternal anterior pituitary is suppressed

The source of estrogen during the second and third trimesters of pregnancy is the (A) corpus luteum (B) maternal ovaries (C) fetal ovaries (D) placenta (E) maternal ovaries and fetal adrenal gland (F) maternal adrenal gland and fetal liver (G) fetal adrenal gland, fetal liver, and placenta