Parathyroid Disorders

Question 1

Calcium in the Body

Answer 1

Adequate calcium levels in the body are dependent on diet
Most calcium is stored in bones and teeth
Plasma calcium:
45% free ionized form
40% bound to protein (albumin)
15% complexed with anions (citrate, phosphate)

Question 2

Calcium functions

Answer 2

Functions:
Build and maintain strong bones and teeth
Smooth muscle contraction
Cofactor for enzymatic reactions
Regulation of clotting mechanisms
Cardiac and nerve function

Question 3

Parathyroid Glands

general
What cell secrets PTH

Answer 3

Four pea-sized glands located posterior to the thyroid gland (superior pair and inferior pair)
Chief cells synthesize, secrete, and store parathyroid hormone (PTH)
Parathyroid hormone regulates calcium levels in the blood through calcium-sensing receptors within the chief cells

Parathyroid Disorders:
Hyperparathyroidism → hypercalcemia
Hypoparathyroidism → hypocalcemia

Question 4

Parathyroid Hormone (PTH)

Functions (3)

Answer 4

Functions:
Increases calcium andphosphate release from the bones through osteoclast activation

Increases calcium reabsorption and phosphate excretion in the distal tubule of the kidney

Increases synthesis of 1,25-dihydroxyvitamin D, (active Vitamin D),which will increase calcium absorption from the gastrointestinal tract

Question 5

Parathyroid Hormone Regulation

Answer 5

Secretion of PTH is stimulated by:
Decreases in serumcalcium
Low levels of 1,25-dihydroxyvitamin D (active form of Vitamin D)
Calcium has a direct relationship with Vitamin D

Hyperphosphatemia
Calcium has an inverse relationship with phosphorus
As levels of phosphorus ↑, the levels of free calcium in the blood decreases, because phosphorus binds to calcium

Hypomagnesemia
Calcium has a direct relationship with magnesium

Secretion of PTH is inhibited by:
High levels of serumcalcium

Question 6

Question 7

Calcitonin

general

Answer 7

Hormone produced by the parafollicular cells (C cells) of the thyroid gland

Secretion of calcitonin is stimulated by:
Increases in serum calcium

directly opposite of PTH

Question 8

calcitonin

Functions (2)

Answer 8

Functions:
1. Inhibits (blocks) the activity of osteoclasts (no calcium is released from bone)
2. Decreases calcium reabsorption in the kidneys

Question 9

Question 10

Question 11

Hyperparathyroidism

general

Answer 11

Condition that results from increased function of the parathyroid glands with overproduction of parathyroid hormone (PTH) → hypercalcemia

Often discovered incidentally when assessing labs

♀>♂
Incidence increases after age 50 years

Question 12

Hyperparathyroidism

types

Answer 12

Primary (Inherent disease of the parathyroid gland)
Secondary
Tertiary

Question 13

Primary Hyperparathyroidism

general and causes

Answer 13

elevated PTH independent of calcium levels

Most common cause
95 % of cases occur sporadically Parathyroid adenoma (benign) ~85%
Parathyroid gland hyperplasia – ~15%
Parathyroid carcinoma – < 1%

5% are familial (genetic mutations) **Multiple Endocrine Neoplasia** I and 4 syndrome

Question 14

Secondary Hyperparathyroidism

general and causes

Answer 14

elevated PTH due to chronic hypocalcemia

Due to an underlying condition that decreases serum calcium levels (abnormal calcium metabolism)
Chronic renal failure (CRF)
Bypass surgery (reduced surface area for absorption of calcium)
Celiac disease/Crohn’s disease (malabsorption)
Severe vitamin D deficiency (low dietary intake, lack of sun exposure, or malabsorption)

Question 15

Tertiary Hyperparathyroidism

general

will not be tested, just know it exists and comes from long standing secondary

Answer 15

Due to long-standing secondary hyperparathyroidism
Hypertrophy and autonomous functioning (unregulated) of the parathyroid glands

Question 16

hyperparathyroidism

clin man

Answer 16

Most patients are asymptomatic or present with nonspecific symptoms

Sx:
Mnemonic: “stones,bones, abdominalgroans, thrones,and psychiatric overtones”
Bone pain
Bone demineralization (osteoporosis) → pathological fractures, cystic bone lesions
Nephrolithiasis (15% of patients)
Renal loss of calcium (calciumphosphate orcalcium oxalate stones)
Abdominal cramps and constipation
Peptic ulcers and pancreatitis
Irritability, confusion, delirium, and depression
Muscle weakness and rapid muscle fatigue
Polydipsia and polyuria
Hypercalcemia-induced nephrogenic diabetes insipidus- dont worry about this
Calciphylaxis
Deposits of calcium in the skin and muscles

Question 17

hyperparathyroidism

Electrocardiogram changes

Answer 17

AV block, short QT interval, Osborn or J waves

Question 18

hyperparathyroidism

Question 19

primary hyperparathyroidism

Serum Labs

calcium, phosphorus, PTH

Answer 19

↑ serum calcium
Measure total serumCa2+if normalalbumin
Measure ionizedCa2+if lowalbumin
↓ or normal serum phosphorus
↑ serum PTH

Question 20

hyperparathyroid

urine labs
Parathyroid cancer indications

Answer 20

↓ urine calcium

24-hour urine for calcium/creatinine ratio required before starting any treatments

Extreme elevations of serum calcium and PTH indicate parathyroid cancer

Question 21

Hyperparathyroidism

EKG

Answer 21

Hypercalcemia

AV block, shortened QT interval
Osborn waves with severe hypercalcemia (>14 mg/dL)

Question 23

hyperparathyroidism

Tx of Asx primary disease

Answer 23

Monitor for the development of symptoms
Monitor serum calcium and albumin levels, calcium excretion, kidney function
Bone density measurements (hip, spine, and forearm) every 1-2 years
Avoid calcium containing antacids and supplements
Maintain adequate Vitamin D intake
Encourage physical activity to decrease bone resorption

Bisphosphonate therapy
Encourage osteoclast destruction → decreased serum calcium levels

Question 24

hyperparathyroidism

Tx of Symptomatic primary disease or presence of parathyroid carcinoma

Answer 24

Parathyroidectomy

Will include an ipsilateralthyroidectomy for those with parathyroid carcinoma

Hypocalcemia and transient hyperthyroidism may occur postoperatively

Question 25

Hypoparathyroidism

general

Answer 25

Condition that results from decreased function of the parathyroid glands with underproduction of parathyroid hormone (PTH) → hypocalcemia

Question 26

hypoparathyroidism

causes (5)

Answer 26

Inadvertent damage (radiation) or removal of thyroid and/or parathyroid glands during neck surgery
Autoimmune disease
Heavy metal toxicity (iron and copper)
Iron overload disorder? Copper overload disorder? HFE!
Hemochromatosis & Wilson’s disease

Thyroiditis
Tissue resistance to PTH (pseudohypoparathyroidism)

Question 27

hypoparathyroidism

clin man and cardiac findings (3)

Answer 27

Symptoms depend on the severity, duration and rate of development

Tetany (increased neuromuscularexcitability):
Mild:
Perioral numbness, muscle cramps/spasms, paresthesias, hyperreflexia
Severe:
Carpopedal spasms, laryngospasm, seizures

Defects affecting the teeth, nails, and hair

Cardiac findings
Prolonged QT interval, arrhythmias, hypotension

Question 28

hypothyroidism

Chvostek sign

Answer 28

Contraction of the eye, mouth, or nose muscles elicited by tapping along the course of the facial nerve anterior to the ear

Question 29

hypothyroidism

Trousseau sign

Answer 29

Spasm in the hand and wrist with compression to the forearm

Question 30

Hypoparathyroidism

Lab findings

Answer 30

↓ PTH
↓ serum calcium
↑ serum phosphorus

Question 31

hypoparathyroidism

EKG

Answer 31

Prolonged QT interval
Arrhythmias

Question 32

Question 33

hypoparathyroidism

Tx of acute severe symptomatic disease
With dosing

Answer 33

Calcium gluconate 1-2 g IV in 50 mL of 5% dextrose (or normal saline) infused over 10-20 minutes (preferred therapy)

Transition to oral calcium supplements

Question 34

hypoparathyroidism

Tx for Mild symptomatic or chronic disease

Answer 34

Oral calcium supplements
Calcium carbonate(orcalcium citrate) 1,500-2,000 mg PO daily in divided doses

Recombinant human PTH

Question 35

Tx of Vitamin D deficiency is the cause of hypocalcemia

Answer 35

Cholecalciferol (vitamin D3) – multiple dosing regimens

Question 36