7 (and 3). Physiologic changes in the renal system and hormonal changes

Question 1

Physical changes to the kidneys and bladder

Answer 1

Progesterone relaxes smooth muscles
Plus the increased possible pressure on the ureters by the uterus
- Causes dilation of the renal pelvis and ureters.
- More pronounced on the right side.

The bladder also dilates and rises.
Its capacity increases from 300-400ml to 1300-1500mL.
- The raised bladder must be accounted for and avoided during C-section.
- Urination increases due to increased kidney output.
-Prior to labor the mother should urinate every hour to prevent the dilated bladder from interfering with birth.

Question 2

Changes in renal function

Answer 2

By 20 weeks,
GFR increases by 50% and plateaus until delivery
Renal blood flow increases by 40% then starts to drop again by about 30 weeks.
Due to relaxation of both the afferent and efferent arterioles.

Serum BUN and Creatinine are Lower than normal.

Glycosuria can normally occur, but if it occurs patient should still be tested for gestational diabetes.

RAAS system is more activated during pregnancy, to stimulate the increased blood volume.
Renin is produced by the kidneys as well as the uterus and placenta.
EPO/Renal Erythropeoitic factor is also increased.

Question 3

Thyroid changes and parathyroid changes

Answer 3

There is mild thyroid enlargement

Increased thyroid-binding globulin protein, so an increase in total thyroid hormone, but levels of free T3 and free T4 remain euthyroid.

BMR increases 10-30%

Serum calcium levels drop mildly due to demand causing increased PTH and increased vitamin D synthesis.
Calcium supplements are recommended. Vit D supplements recommended for vegetarians.

Question 4

Changes of hCG, progesterone, and estrogen.

Answer 4

hCG is made by placental trophoblasts

• detectable by 1 week embryonic age in the serum, 2 weeks in the urine, or by 4 weeks gestational age in the urine.
• doubles every 48 hours until peak.
• peaks at 10 weeks and then drops to a low plateau by about 20 weeks.
• maintains corpus luteum to maintain progesterone secretion until the placenta has grown enough to maintain progesterone.

Progesterone, made by corpus leuteum then placenta
- Steady increases until birth.

Estrogen, made by both the placenta and fetus. Primarily in the form of Estriol, E3.

• Increases uterine blood flow and growth.
• Stimulates breast growth
• Increases steadily until birth

Question 5

What are the other major hormones of pregnancy and how do they change

Answer 5

Human placental lactogen, hPL.

• made by placenta
• levels of hPL parallel placental growth.
• Inhibits Insulin action, to increase glucose availability to fetus.
• Low hPL levels inciate threatened abortion or IUGR.

CRH, Corticotropin releasing hormone

• Made by the placenta
• stimulates fetal ACTH secretion and DHEA production, a needed precursor for fetal and placental estrogen synthesis.

Prolactin
- PRL levels increase in pregnancy, stimulates breads gland and milk production

Relaxin

• from the corpus luteum and placenta
• softening of the cervix and pubic symphysis
• promotes implantation

Oxytocin

• Released from from neurohypophysis when stimulated by birth canal stretching and by nipple stimulation.
• Causes uterine contractions and stimulates milk let down from the breasts.