Fa: Endocrine - Embryology, Anatomy, & Physiology -4

Front 1

What is the source of Parathyroid Hormone (PTH)?

Back 1

Chief cells of parathyroid gland

Front 2

What are the effects of PTH?

Back 2

- ↑ Bone resorption of Ca2+ and PO4(3-)
- ↑ Kidney reabsorption of Ca2+ in distal convoluted tubule
- ↓ Reabsorption of PO4(3-) in proximal convoluted tubule
- ↑ 1,25-(OH)2-D3 (Calcitriol) production by stimulating kidney 1α-hydroxylase

Front 3

How does PTH affect the nephron? Which parts?

Back 3

- ↑ Kidney reabsorption of Ca2+ in distal convoluted tubule
- ↓ Reabsorption of PO4(3-) in proximal convoluted tubule

Front 4

How does PTH affect the bones?

Back 4

↑ Bone resorption of Ca2+ and PO4(3-)

- ↑ Production of macrophage colony-stimulating factor and RANK-L (receptor activator of NF-κB ligand)
- RANK-L secreted by osteoblasts and osteocytes binds RANK (receptor) on osteoclasts and their precursors → stimulates osteoclasts and ↑ Ca2+

Front 5

How does PTH affect the kidney, besides its action on the nephron?

Back 5

↑ 1,25-(OH)2-D3 (Calcitriol) production by stimulating kidney 1α-hydroxylase

Front 6

Which enzyme produces 1,25-(OH)2-D3 (calcitriol) in the kidney?

Back 6

1α-Hydroxylase

Front 7

What is the net effect of PTH on Ca2+ and PO4(3-) in the serum and urine?

Back 7

- ↑ Serum Ca2+
- ↓ Urine Ca2+

- ↓ Serum PO4(3-)
- ↑ Urine PO4(3-)

(Phosphate Trashing Hormone = PTH)

Front 8

What peptide is similar to PTH? Source?

Back 8

PTH-related peptide (PTHrP)
- Functions like PTH
- Commonly ↑ in malignancies (eg, paraneoplastic syndrome)

Front 9

How is PTH regulated?

Back 9

- ↓ Serum Ca2+ → ↑ PTH

- ↓ Serum Mg2+ → ↑ PTH
- ↓↓ Serum Mg2+ → ↓ PTH

Front 10

What are common causes of ↓ Mg2+?

Back 10

- Diarrhea
- Aminoglycosides
- Diuretics
- Alcohol abuse

Front 11

What is the effect of PTH on the intestine?

Back 11

- Increases intestinal Ca2+ absorption
- Increases intestinal PO4(3-) absorption

Front 12

What are the forms of calcium in the plasma? What percent is in each form?

Back 12

- Ionized (~45%)
- Bound to albumin (~40%)
- Bound to anions (~15%)

Front 13

How does pH affect calcium homeostasis in the plasma?

Back 13

↑ in pH → ↑ affinity of albumin (negative charge) to bind Ca2+

Clinical manifestations of hypocalcemia:
- Cramps
- Pain
- Paresthesias
- Carpopedal spasm

Front 14

What are the sources of Vitamin D? Activation?

Back 14

- D3 from sun exposure in skin
- D2 ingested from plants

- Both converted to 25-OH in liver and to 1,25-(OH)2 (active form) in kidney

- 24,25-(OH)2-D3 is an inactive form

Front 15

What is the function of Vitamin D (Cholecalciferol)?

Back 15

- ↑ Absorption of dietary Ca2+ and PO4(3-)
- ↑ Bone resorption → ↑ Ca2+ and PO4(3-)

Front 16

How is Vitamin D regulated?

Back 16

- Increased 1,25-(OH)2-D production by: ↑ PTH, ↓ [Ca2+], ↓ [PO4(3-)]

- 1,25-(OH)2 feedback inhibits its own production

Front 17

What are the implications of a deficiency of Vitamin D?

Back 17

- Rickets in kids
- Osteomalacia in adults

Front 18

What can cause a Vitamin D deficiency?

Back 18

- Malabsorption
- ↓ Sunlight
- Poor diet
- Chronic kidney failure

Front 19

What is the source of Calcitonin?

Back 19

Parafollicular cells (C cells) of Thyroid

Front 20

What is the function of Calcitonin?

Back 20

↓ Bone resorption of Ca2+ → Tones down Ca2+ levels

Front 21

What regulates Calcitonin?

Back 21

↑ Serum Ca2+ causes Calcitonin secretion (to tone down Ca2+ levels in serum)

Front 22

How do PTH and Calcitonin relate?

Back 22

- Calcitonin opposes actions of PTH
- Calcitonin is not important in normal Ca2+ homeostasis

Front 23

Which endocrine hormones signal via "cAMP"?

Back 23

FLAT ChAMP + CGG:
- FSH
- LH
- ACTH
- TSH

- CRH
- hCG
- ADH (V2 receptor)
- MSH
- PTH

- Calcitonin
- GHRH
- Glucagon

Front 24

Which endocrine hormones signal via "cGMP"?

Back 24

Think vasodilators:
- ANP
- NO (EDRF)

Front 25

Which endocrine hormones signal via "IP3"?

Back 25

GOAT HAG:
- GnRH
- Oxytocin
- ADH (V1 receptor)
- TRH

- Histamine (H1 receptor)
- Angiotensin II
- Gastrin

Front 26

Which endocrine hormones signal via "steroid receptors"?

Back 26

VETTT CAP:
- Vitamin D
- Estrogen
- Testosterone
- T3 and T4

- Cortisol
- Aldosterone
- Progesterone

Front 27

Which endocrine hormones signal via "intrinsic tyrosine kinase"?

Back 27

MAP kinase pathway, think growth factors
- Insulin
- IGF-1
- FGF
- PDGF
- EGF

Front 28

Which endocrine hormones signal via "receptor-associated tyrosine kinase"?

Back 28

JAK/STAT pathway, think acidophiles and cytokines (PIG)
- Prolactin
- Immunomodulators: IL-2, IL-6, IL-8, IFN
- GH

Front 29

What kind of signaling pathway is important for the MAP kinase pathway?

Back 29

Intrinsic tyrosine kinase

Front 30

What kind of signaling pathway is important for the JAK?STAT kinase pathway?

Back 30

Receptor-associated tyrosine kinase

Front 31

What is the signaling pathway of steroid hormones?

Back 31

- Steroid hormone binds to receptor located in nucleus or cytoplasm
- Transformation of receptor to expose DNA-binding domain
- Enters cell and binds to enhancer-like element in DNA
- Affects gene transcription: pre-mRNA → mRNA → protein → response

Front 32

What happens to steroid hormones in the serum? Why?

Back 32

Steroid hormones are lipophilic and therefore must circulate bound to specific binding globulins, which ↑ their solubility

Front 33

What happens to men with increased sex-hormone binding globulin (SHBG)?

Back 33

Gynecomastia

Front 34

What happens to women with increased sex-hormone binding globulin (SHBG)?

Back 34

Hirsutism

Front 35

What can increase the amount of sex-hormone binding globulin (SHBG)?

Back 35

- OCPs
- Pregnancy

(Free estrogen levels remain unchanged)