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Endocrine Physiology: CaseEndocrine Physiology: Case
Studies in Calcium MetabolismStudies in Calcium Metabolism
C.W. Spellman PhD, DOC.W. Spellman PhD, DO
Assoc. Prof. MedicineAssoc. Prof. Medicine
Assist. Dean, Dual Degree ProgramAssist. Dean, Dual Degree
ProgramHead, Endocrinology & Dir. Diabetes ClinicsHead,
Endocrinology & Dir. Diabetes Clinics
UNTHSCUNTHSC
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Normal Values
Ca 8.4 - 10.6 mg/dL
PO4 2.5 - 4.5 mg/dL
Mg 1.5 - 2.5 mg/dl
Creat 0.6 - 1.3 mg/dL
BUN 8 - 12 mg/dL
Alb 3.5 - 4.5 mg/dLTSH 0.3 - 5.0 mIU/ml
iPTH 15 - 50 pg/ml
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Review: Basic Metabolic Control
of Calcium Metabolism
Low calcium: + PTH
High calcium: - PTH
PTH: + renal calcium resorption
+ renal phosphate excretion
+ renal 1,25 Vit D3 synthesis
+ calcium resorption from bone Vit D3: + gut absorption of
calcium
+ gut absorption of phosphate
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Signs and Symptoms of Hypercalcemia
Hypercalcemia may present with vague Si/Sx
Si/Sx are quite variable
Ill-defined correlation's of symptoms withdegree of
hypercalcemia
Most common presentation: Asymptomatic
Calcium 12 mg/dL may present withFatigue
Depression
Headache
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Signs and Symptoms ofHypercalcemia
If calcium is > 12 mg/dl, one may see:
Neurol Lethargy, confusion, coma
Psych Depression, psychosisCardiol Hypertension
Nephrol DI, nephrolithiasis
GI Nausea/emesis, PUD, anorexiaConstipation, pancreatitis
Rheum Proximal weakness, bone loss
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Causes of Hypercalcemia Differential diagnosis of
hypercalcemia
Increased PTH production
Production of PTH-like hormone
Production of Vit D-like factors
Drugs
Familial disorders
Diseases affecting calcium metabolism
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Hypercalcemia: Elevated PTH Primary elevation of PTH:
85% parathyroid adenoma
10% parathyroid hyperplasia(3% MEN)
2% parathyroid carcinoma
Secondary elevation of PTH
Renal failure
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Hypercalcemia: Other causes
PTH-related peptide (cancers)
Breast, lung, renal
Thyroid
Lymphoma, Leukemia, Myeloma
Vit-D3-like factors (granulomatous dz)
TBHistoplasmosis
Sarcoidosis
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Hypercalcemia: Other Causes
Drugs
Lithium
Antacids
Calcium
Thiazides
Vit-D intoxication
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Hypercalcemia: Other Causes
Other diseases
HyperthyroidismPagets
FHH syndrome
Immobility
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Signs and Symptoms ofHypocalcemia
Findings may include:
Neurol Trousseaus (carpopedal spasm)
Chvosteks (CN VII spasm)Paresthesias, tetany
Lethargy, seizures
Respiratory arrest
Cardio Heart block, CHF
Rheum Weakness, cramps
Derm Dry skin, brittle hair
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Causes of Hypocalcemia PTH absent
a. Hypoparathyroidism (hereditary)
b. Acquired hypoparathyroidism
Surgery (thyroid, parathyroid)
Autoimmune disease
Autoimmune parathyroid destruction
PGA-1, PA, Hashimotos, T1DMInfiltrative disease
Metastatic dz
Alcohol (q
PTH release, 20
to(
Mg)
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Causes of Hypocalcemia PTH absent, cont.
Hypomagnesemia
a. q PTH release
b. q PTH responsiveness
PTH ineffectiveChronic renal failure
a. q Vit-D 1,25 synthesis
b. PO4 retentionq PTH effects on bone
qVit-D 1,25 synthesis
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Causes of Hypocalcemia
PTH ineffective, cont.
Dietary Vit-D deficiency
Gut malabsorption of Vit-D
q Sun light exposureAnti-convulsants
o hepatic degradation of Vit-D
Vit-D resistancePseudohypoparathyroidism
Defective PTH receptor
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Causes of Hypocalcemia
PTH overwhelmed
Severe, rapid loss of calcium from ECF
a. Acute renal failure
b. Tissue destruction
Rhabdomyolysis
Tumor lysis
Pancreatitis
c. Hungry bone syndromes/p parathyroidectomy
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Causes of Hypocalcemia
PTH overwhelmed: Mechanismsa. Acute renal failure, tissue
destruction
Decreased renal PO4 excretion
Rapid cellular release of PO4
p Acute hyperphosphatemia
p urinary calcium loss
p Hypocalcemia
b. s/p resection of parathyroid tumorp Sudden decrease serum
PTH
p Rapid bone uptake of calcium
p
Hypocalcemia
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Case 1: New Patient With Elevated
Serum Calcium
40 yr male is seen as a new patient to
establish care. He has no complaints.
PMHx is negative
Baseline laboratory studies are significant
for serum calcium of 11.5 mg/dL
Physical examination is normal
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Case 1, Questions
What is the most common cause ofasymptomatic hypercalcemia?
This patients iPTH would be
a. Highb. Normalc. Low
This patients PO4 would be
a. High
b. Normalc. Low
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Case 2: Man With Lethargy,
Fatigue and Weakness
60 yr old male presents with complaints
of fatigue and weakness over 1 month.
PMHx: Negative
PE: significant for memory and cognitive
defects
Lab: Ca 15.0 mg/dL
PO4 2.3 mg/dL
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Case 2, Questions
Predict the iPTH values if this patients
hypercalcemia was due to:
a. Primary hyperparathyroidism
b. Malignancy
c. Vit D intoxication
d. Granulomatous disease
e. Hyperthyroidism
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Case3: Lady With Back Pain
75 yr old lady presents with complaints of
low back pain.
PMHx: TAH-BSO @ age 35
No HRT
HTN
Hypothyroid
Meds: Verapamil, levothyroxine
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Case 3, cont.
PE: Thin, kyphotic
Lab: Ca 9.2 mg/dL
BUN/Creat 8/0.9 mg/dL
TSH 2.1 mIU/ml
Imaging studies:
CT: Compression fractures T
and L spineDEXA: Loss of bone density
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Case 3, Questions
Which of the following is most likely tobe found?
a. Hypophosphatemia
b. Hyperphosphatemia
c. Low Vit D3
d. High Vit D3
e. Low alkaline phosphatase
f. High alkaline phosphatase
g. None of the above
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Case 4: Child With Poor SchoolPerformance
14 yr old boy is evaluated for poor school
performance.
PMHx: Unremarkable
PE: Lethargic, DTRs 3+
Lab: Ca 5.1 mg/dL
PO4 7.5 mg/dL
Renal function = normal
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Case 4, Questions
Possible causes of this patients hypocalcemia:
Hypoparathyroidism?Low calcium intake?
Pseudohypoparathyroidism?
Vit D deficiency?
