Parathyroid glands

• 4 glands located near the thyroid

• PTH – polypeptide

• Regulates calcium homeostasis

• Defends against hypocalcemia

• Stimulates bone resorption by osteoclasts

• Stimulates renal tubular reabsorption of Ca

• Inhibits renal tubular reabsorption of phosphate

• Stimulates synthesis of the active form of vit D

Hypercalcemia

2.25 – 2.75 mmol/l

Causes:

primary hyperparathyroidism

Malignant diseases – osteolytic MT, hematologic

malignancies – producing PTHrp

Sarcoidosis, tbc, thyrotoxicosis

Drug induced – vit D,A, thiazide..

Immobilisation

Familial, ARI, CHRI

Primary hyperparathyroidism

-PTH is secreted inappropriately despite an elevation of

serum Ca

-Incidence: 20-40 ties, more common in women

-Etiology: parathyroid adenoma – 85%

hyperplasia – 15%

familial, part of MEN syndrome

Histopatologic types of PHPT

Sosa JA, Udelsman R Curr Probl Surg. 2003;40:812-849

85% 15% < 1%

adenoma hyperplasia carcinoma

Primary hyperparathyroidism

Symptoms:

Asymptomatic – majority patients

Fatigue, weakness, arthralgias, polyuria, constipation, nausea

CNS: lethargy, depression,. Confusion, stupor, coma

Kidney stones – calcium oxalate, calcium phosphate

CVS: arterial hypertension, short QT interval, bradycradia,

increased sensitivity to digitalis.

GIT: peptic ulcer disease, pancreatitis,

Bone disease

Primary hyperparathyroidism

Investigations

S-Ca elevated, S-P decreased, U-Ca increased, U-P increased

ALP normal/elevated

Dihydroxy vit D – elevated

PTH – elevated

X ray: osteitis fibrosa cystica, osteopenia, osteoporosis,

subperiostal bone resorption of the distal phalanges

DXA: disproportional loss of cortical bone

Primary hyperparathyroidism

Imaging methods:

US, CT, MIBI scintigraphy

Treatment:

Surgical removal of abnormal gland or glands.

Radioablation

Injection of etanol under US

Hypercalcemia of malignancy

Breast ca, lung, kidney

Hematologic malignancies, myeloma, T cell lymphomas

Mechanisms of hypercalcemia:

Localized bone destruction:

PTHrP – paraneoplastic production

Treatment of hypercalcemia

1. Hydration

2. Furosemide

3. Glucocorticoids – not effective in PHPT, sarcoidosis,

myeloma..

4. Calcitonin – inhibits osteoclastic resorption (s.c., i.m.)

5. Phosphate

6. Bisphosphonates – inhibit bone resorption

7. Acute severe hypercalcemia – hemodialysis

8. Calcimimetics - cinacalcet

Hypocalcemia

Abnormal reduction in serum ionized calcium concentration.

Etiology:

Hypoparathyroidism hungry bone syndrome

PTH resistance osteoblastic MT

Vitamin D deficiency acute pancreatitis

Vitamin D resistance

CHRF

Hypoparathyroidism

-surgical removal of PT during thyroidectomy

-Idiopathic- autoimmune ??

-Post neck iradiation

-PTH resistance - pseudohypoparathyroidism

Hypoparathyroidism

Symptoms:

often asymptomatic

Neuromuscular irritability: paresthesias, carpal pedal spasms

Laryngospasm, tetany

CNS: seizures, EEG, increased intracranial pressure

CV: prolonged QT, congestive heart failure

Other: abnormalities of teeth, skin, hair, cataract

Hypoparathyroidism

Chvostek sign: switching of the facial muscles following tapping

of the facial nerve

Laboratory manifestations:

Hypocalcemia, hyperphosphatemia

Low PTH levels

High PTH – pseudohypoparathyroidism

X ray: calcifications in basal ganglia

Hypoparathyroidism

Treatment:

Calcium

Vitamin D therapy

Acute: Calcium gluconicum i.v.

Chronic: Ca + vitamin D