2-6: 5/26: Hypocalcemia, Hypoparathyroidism, Vitamin D Deficiency

Front 1

PTH Effects:
Bone
Kidney

Back 1

Bone: Calcium and PO4 resorption (release)

Kidney: Calcium reabsorption; PO4 excretion; 25 Vit D (inactive)-->1,25 Vit D (Active)

Front 2

_________ triggers the release of PTH.

Back 2

Decrease in serum calcium

Front 3

1,25 Vitamin D Effects:
Intestines
Kidney

Back 3

Intestines: calcium and PO4 reabsorption from gut

Kidney: PO4 reabsorption

Front 4

The conversion of 25 Vit D to 1,25 Vit D is INHIBITED by ________.

Back 4

HIGH PO4 concentrations (thus preventing Ca and PO4 reabsorption from gut then PTH release)

Front 5

Where are calcium sensing receptors located?

Back 5

Parathyroid Gland (PTH secretion)
Loop of Henle (Ca secretion from renal tubules)

Front 6

What is the 'setpoint' for calcium?

Back 6

8.5

Front 7

What are the main causes of hypoparathyroidism?

What lab values correlate with each cause?

When would hungry bone be present?

Back 7

-No parathyroid gland (low PTH; low Ca and High/LOW PO4; IF LOW PO4-->HUNGRY BONE)
-No PTH production/secretion (low; PTH; low Ca, High PO4)
-PTH resistance (receptor level; HIGH PTH; low Ca and high PO4)

Front 8

DiGeorge Syndrome

Back 8

Congenital (no Parathyroid Gland)

Front 9

Most common disorder of parathyroid gland?

Back 9

Irradiation of neck (thyroid usually)

Front 10

A manipulation of blood supply (to the thyroid region) could result in _____.

Back 10

Transient hypoparathyroidism

Front 11

What is hungry bone syndrome?

Back 11

Inc'd rate of bone resorption as a result of hypoparathyroidism

When you do a thyroidectomy, bone wants to remineralize, and HOGS up all serum Ca, PO4, Mg

Front 12

What is the effect of a transient activating Ca-SR antibody?

Back 12

Not destructive, but results in decreased PTH secretion

Front 13

Mutation in preproPTH results in _______.

Back 13

Abnormal PTH synthesis (hypopara)

Front 14

What is the effect of an activating mutation to CaSR on the calcium set point?

Back 14

Lower set point (requires lower Ca2+ concentration to activate)

Front 15

Mutation in GNAS1 results in ______.

Back 15

PTH Resistance (receptors don't bind PTH)-->hypopara

Front 16

Albright's Hereditary Osteodystrophy:
Symptoms
Cause

Back 16

Round facies
Short stature
Short fourth metacarpals
obesity
Subcut calcifications
Developmental delay

Cause: PTH resistance (maternal transmission)

(If paternally transmitted would be pseudopseudohypoparathyroidism)

Front 17

Vitamin D:
Sources

Back 17

Sunlight (7-dehydrocholesterol-->Cholecalciferol--Vit D3)

Diet: D3, D2

Front 18

Effect of LOW Vitamin D on:
GI
Parathyroid Gland
Bone
Kidney

Back 18

GI: decreased Ca and PO4 absorption

Parathy: Increase PTH

Bone: increase resorption

Kidney: increase Ca resorption

Front 19

How does low vitamin D result in Osteomalacia/Rickets?

Osteomalacia vs Rickets?

Back 19

Bone growth and mineralization requires Ca and PO4

Low Vit D-->Low Ca and PO4

Osteomalacia: impaired mineralization of bone matrix (ADULTS)

Rickets: Deficient mineralization of growth plate cartilage (CHILDREN); chondrocytes get resorbed!

Front 20

Extraskeletal manifestations of Vit D deficiency.

Back 20

Delay of motor milestones
Dec'd muscle tone
Wasting
Proximal mm weakness
Waddling gait
Seizures
Hypoplasia of dental enamel
Dentin defects (abscess and decay)

Front 21

Vitamin D Deficiency:
Causes

Back 21

-Deficient uptake, absorption (diet, sun exposure)
-Defective 25-hydroxylation (liver issue; anticonvulsants)
-Defective 1-alpha-25-hyrdoxylation (hypopara, renal failure, enzyme defect)
-Vitamin D Receptor defect (VDDR-2)

Front 22

1-alpha hydroxylase deficiency results in ________.

Back 22

Defect in D25-->D1,25

Front 23

What is Vitamin D-Dependent Rickets Type II?

Back 23

Hereditary Vitamin D-resistant Rickets (mutation to vit D receptor)

More alopecia-->more severe disease

Front 24

What type of vitamin D is present in PO supplements? Requirement?

Back 24

D2 (cholecalciferol)/D3 (ergocalciferol)
Both require hepatic hydroxylation to calcitriol (need functional liver!)

D3 (ergocalciferol) is more potent; used in Rickets and osteomalacia

Front 25

What Vitamin D supplement is best for a patient with renal failure?

Back 25

1,25-OHD (Calcitriol)

Don't need a liver either!

Front 26

A patient presents with signs of osteomalacia/Rickets.

What tests do you run to find the cause?

Back 26

Measure 25-OH D
If low-->Vit D Deficiency
If normal, measure 1,25-OH D

If 1,25-OH D Low-->defect in 1-alpha hydroxylase (can't convert 25-->1,25)
If high-->dysfn of Vit D Receptor (have working enzyme)

Front 27

Extravascular Deposits of Calcium:
Causes

Back 27

Hyperphosphatemia (renal failure, excess intake)

Osteoblastic mets (BrCa, ProsCa)

Acute pancreatitis

Hungry bone post-parathyroidectomy

Front 28

Intravascular Complexing of Calcium:
Causes

Back 28

Chelators (Citrate, Lactate)--bind Ca and ionized levels drop

Alkalosis

Front 29

Effect of magnesium levels on PTH.

Back 29

Hypomagnesemia-->PTH resistance, reduced secretion (assocd w/malabsorption, EtOH, diuretics, etc)

Hypermanesemia: Suppress PTH secretion

Front 30

Hypocalcemia:
Causes
Symptoms

Back 30

Hypoparathyroidism
Vitamin D Def
Low of Calcium from circulation
Disorders of Mg

Syx:
-Tetany, twitching, seizures
-CV: prolonged QT, arrythmia
-Chovstek's Sign
-Trousseau's Sign

Front 31

What is Chovstek's sign and what does it indicate?

Back 31

Tap facial nerve-->muscle contracts

HYPOCALCEMIA

Front 32

What is Trousseau's sign and what does it indicate?

Back 32

Put on BP cuff-->forearm contracts

HYPOCALCEMIA

Front 33

Total Calcium is a measure of _____.

Back 33

Calcium bound to protein (albumin) -45%
Calcium bound to anion (phosphate, citrate)-15%
Free or ionized calcium-40%

Front 34

In a critically ill patient with hypocalcemia, what test would you order?

Back 34

IONIZED calcium (calcium-albumin complex altered by pH; acidosis reduces binding, alkalosis increases binding)

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