Monday Megans Sections
Summer Session Handout 5
Topics: Endocrinology of Pregnancy; Sexual Development; Pancreatic Hormones; Insulin
Secretion and Transduction Pathways, Actions
Endocrinology of Pregnancy: hCG, relaxin, estrogen, progesterone, prolactin, and other
hormones all
hCG
o LH-like
o Sustains corpus luteum up until the 2nd trimester, though it is present throughout
pregnancy
o Keeps estrogen and progesterone levels up
hPL (human placental lactogen)
o secreted by the placenta
o growth hormone of pregnancy
o mainly effects on the mother because it doesnt cross the placenta
o decreases glucose utilization (increases insulin resistance)increase in
circulating glucose, can contribute to gestational diabetes
o increases lipolysis to increase FA in the blood (for the same purpose)
o increases amino acids
purpose is to increase delivery of glucose, FA, and amino acids to the baby
to help it grow
relaxin
o secreted by the placenta
o causes relaxation of the ligaments in the pelvis
o decreases the excitability of the uterine smooth muscle (inhibits contractility)
o decreases number of oxytocin receptors
progesterone and 17-OH-progesterone
o also decrease excitability and contractility of the uterus
o 17-OH-progesterone is sometimes prescribed to prevent early delivery
Estrogen, estradiol
o DHEA-S(made in fetus and moms adrenals) DHEA androstenedione
testosterone estrogen (placenta and ovaries have aromatase)
o Estrogen increases dramatically during pregnancy and has several effects
Increases growth and excitability of the myometrium
Increases oxytocin receptors
However, these two effects are overridden by the effects of relaxin
and progesterone
Increases growth of the breasts and prepares the breast to make milk,
along with prolactin
However, it prevents milk production until after delivery when
placenta loss causes a dramatic drop in estrogen levels
Labor and Delivery (Partruition): CRH, Oxytocin
Estrogen effects: female pubertymenopause
Secondary sex characteristics
Increase breast size, hips width and size, and glutei
Increase in female pattern pubic hair, axillary hair
Sebaceous gland stimulationacne
Increases libido
Increases myometrium and endometrium of uterus
Stimulates exocrine glandsvagina, genitalia
Mucus fluid, elastic, ferning
Growth spurt
o Sealing of epiphyseal plates
Increases pigment of areolae and genitalia
Increase the HDL, decrease the LDL
Increase mineralization of bone (decreases resorption)
Increases blood clotting
increases sweating with body odor
QuestionsPregnancy and Menstruation
1. Why is progesterone essential for pregnancy?
2. What hormonal change causes menstruation if the oocyte is not fertilized?
3. What causes morning sickness?
4. What hormone preserves the corpus luteum? What secretes it?
5. What are the effects of hPL? How do its levels vary during pregnancy?
6. How does relaxin prepare the mothers body for delivery of the baby?
7. What hormone is sometimes used to prevent premature birth by inhibiting contractility of
the uterus?
8. Nearly all hormones are at elevated levels during pregnancy. Name two besides those
mentioned previously.
9. What stimulates the increase of PRL levels after delivery of the baby?
------------------------------------------------------------------------------------------------------------------------------Pancreatic Hormones: Insulin and glucagon
Alpha (Gcg)
cellsglucagon Beta cellsinsulin (Ins)
Delta cellssomatostatin (Sst)
Insulin and glucagon act in sort of a yin-yang mechanism, balancing one anothers effects
to maintain normal levels of glucose in the blood
o Normal glucose levels: 70-110 mg/dL
o Hypoglycemia: <70 mg/dL
o Hyperglycemia: >110 mg/dL
Glucagon: fasting state, hypoglycemia
Stimuli
o Decrease in blood glucose
o Activation of the sympathetic nervous system
to some extent activation of parasympathetic, but not as much
Inhibitors
o Insulin
o Somatostatin
o Increased blood glucose levels, like after a meal rich in carbohydrates
Effects
o Activates Gs receptor
o Liver: increases glycogen phosphorylase kinase levelsincreases activity of
glycogen phosphorylase breaks down glycogen to get glucose phosphate and
ADPglucose-6-phosphatasecatalyzes G-6-P + H2Oglucose +
Piincreases concentration of glucose in liver cellsGLUT 2 transporter
o Increase in hormone sensitive lipase activity in adipocytes
Triglycerides and H2Oglycerol and 3 FAs
o Over long-term starvation, can increase breakdown of proteins, as well as
promote gluconeogenesis
Glucose transporters
o GLUT 2liver, beta cells of pancreas, kidney proximal tubules, intestines; low
affinity for glucose
o GLUT 3neurons; high affinity for glucose
o GLUT 1most cells; medium affinity for glucose
o GLUT 4skeletal muscles and adipose tissue; insulin dependent except in
exercising muscle
Insulin: fed state
C-peptide is attached to insulin before being activated; c-peptide is longer-lasting in the
circulation and is used as a measurement of the levels of insulin being secreted
Stimuli/Secretion mechanism
o Increase in blood glucosebeta cell GLUT2 uptakeincrease ATP levels in the
cell beta cells have K+ channels that are ATP gated, which are normally open
and allow K+ to leak out without high levels of ATPATP floods in and blocks
these channels depolarization opens voltage-gated Ca2+ channels
increases intracellular Ca2+ exocytosis of secretory vesicles containing insulin
Earliest drugs that promote insulin secretion were sulfonyl ureas, which
mimicked blocking of KATP channels to promote insulin secretion
o GLP-1, GIP
Help to stimulate insulin secretion
Presence of food in the stomach stimulates their secretion to prepare for
the secretion of insulin, which needs to happen as soon as glucose from a
meal begins to enter the circulation
Beta cells have GPCR, which recognize GLP-1 and GIP
Also known as incretins
Analogs have been used to treat type 2 diabetes
o Glucagon also helps to promote insulin secretion (think yin-yang effect) because
glucagon puts glucose into blood, while insulin sort of acts as the key that helps
the cells to utilize it
o Parasympathetic activity also stimulates
Diabetes mellitus types 1 and 2 will be next lecture.
Questions: Pancreatic Hormones; Insulin Secretion and Transduction Pathways, Actions
10. What are the types of cells in the pancreas that secrete hormones and what hormones do
they secrete?
11. Describe the mechanism of insulin secretion.
12. Sulfonyl ureas are drugs used to treat Type 2 Diabetes. How do sulfonyl ureas act?
13. What are the stimuli of insulin secretion?
14. Normal blood glucose level range:
Hyperglycemic:
Hypoglycemic:
15. What inhibits beta cell activity?
16. What are the different glucose transporters? What are their sensitivities to glucose in
terms of affinity?