Endocrine System

In general, the endocrine system is modified in the pregnancy state by the addition of the fetoplacental unit. The fetoplacental unit produces human chorionic gonadotropin (hCG) and human placental lactogen (hPL) among other hormones.

■ hCG (luteotropic): Coregulates and stimulates adrenal and placental steroidogenesis. Stimulates fetal testes to secrete testerone. Possesses thyrotrophic activity.

■ hPL (also called human chorionic somatomammotropin [hCS]): Antiinsulin and growth hormone-like effects ^ impaired maternal glucose and free fatty acid release.

Pituitary Gland

Pituitary gland increases in weight and sensitivity.

Prolactin

■ Plasma levels rise within a few days postconception.

■ At term, levels are 10- to 20-fold higher than nonpregnant state.

Hemodilution is not due to a fall in total circulating hemoglobin.

An apparent anemia may be a sign of good physiologic adaptation to pregnancy, while an elevated hemoglobin may represent pathology (i.e., hemoconcentration in pregnancy-induced hypertension).

Follicle-Stimulating Hormone

■ Blunted response to gonadotropin-releasing hormone (GnRH)

■ Shows a progressive decreased response ^ no response at 3 weeks after ovulation o

The pregnant female is more susceptible to viral infections, malaria, and leprosy.

The fetoplacental unit produces hCG and hPL.

Pregnancy andcombinations of estrogen and progestational agents (i.e., OCs and HRT) are the most frequent causes of melasma (often called the "mask of pregnancy").

Luteinizing Hormone

■ Response to GnRH diminishes and finally disappears.

Adrenal Gland

■ Plasma Cortisol and other corticosteroids increase progressively from 12 weeks to term and reach 3 to 5 times nonpregnant levels.

■ Half-life of plasma cortisol is increased, while its clearance is reduced.

Thyroid Gland

The following changes are thought to be due to the increase in estrogen during pregnancy:

■ Increases in size during pregnancy

■ Total thyroxine levels and thyroxine-binding globulin increase. The result is that free thyroxine remains normal and the mother remains euthyroid.

Parathyroid Glands

■ Parathyroid hormone levels increase in pregnancy, which increases maternal calcium absorption, to offset maternal losses across the placenta to the fetus.

■ At term, serum parathyroid hormone levels are higher in the mother, but calcitonin is higher in the fetus. This results in fetal bone deposition.

Plasma Proteins

Concentrations of proteins in maternal serum fall markedly by 20 weeks, mostly due to a fall in serum albumin. This fall reduces the colloid osmotic pressure in the plasma ^ edema in pregnancy.

Pancreas

■ Size of islets of Langerhans increases during pregnancy.

■ The number of beta cells increases during pregnancy.

■ The number of insulin receptor sites increases during pregnancy.

Insulin

■ Serum levels rise during second half of pregnancy, but insulin resistance increases as well.

■ This insulin resistance may be due to presence of hPL, prolactin, or other pregnancy hormones that have anti-insulin activity.

Glucagon

■ Levels are slightly raised in pregnancy, but not as much as insulin levels.

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