Hypoparathyroidism/Hyperparathyroidism

Question 1

Where are the parathyroid glands located?

Answer 1

There are normally four parathyroid glands located behind the
thyroid gland. There are two superior glands and two inferior
glands. They are typically around 6 mm long and about 3
millimeters wide.
Guyton AC, & Hall, JE. Textbook of Medical Physiology. 12th
ed. Philadelphia: Saunders; 2011: 962.

Question 2

What are the two types of cells found in the

parathyroid glands?

Answer 2

The two major types of cells are the chief cells, which secrete
parathyroid hormone, and oxyphil cells. The function of oxyphil
cells is not known, but it is believed that they may be depleted
chief cells that no longer secrete the hormone.
Guyton AC, & Hall, JE. Textbook of Medical Physiology. 12th
ed. Philadelphia: Saunders; 2011: 963.

Question 3

What is the principal function of the parathyroid

glands?

Answer 3

The parathyroid glands release parathyroid hormone which
regulates calcium balance.
Butterworth JF, Mackey DC, Wasnick JD. Morgan & Mikhail’s
Clinical Anesthesiology. 5th ed. New York, NY: McGraw-Hill;
2013: 736.

Question 4

How does parathyroid hormone increase serum

calcium levels?

Answer 4

Parathyroid hormone increases serum calcium levels by
increasing bone resorption of calcium, limiting its renal
excretion, and enhancing the gastrointestinal absorption of
calcium by regulating vitamin D metabolism.
Butterworth JF, Mackey DC, Wasnick JD. Morgan & Mikhail’s
Clinical Anesthesiology. 5th ed. New York, NY: McGraw-Hill;
2013: 736.

Question 5

How does parathyroid hormone decrease serum

phosphate?

Answer 5

By increasing the renal excretion of phosphate.
Butterworth JF, Mackey DC, Wasnick JD. Morgan & Mikhail’s
Clinical Anesthesiology. 5th ed. New York, NY: McGraw-Hill;
2013: 736.

Question 6

What types of factors would increase the release of

parathyroid hormone?

Answer 6

Any condition that results in even a slight decrease in calcium
ion concentration in the extracellular fluid will stimulate the
release of parathyroid hormone. The parathyroid glands
become hyperactive and hypertrophied in conditions such as
rickets, pregnancy, and lactation.
Guyton AC, & Hall, JE. Textbook of Medical Physiology. 12th
ed. Philadelphia: Saunders; 2011: 965.

Question 7

What are some conditions that would cause the
parathyroid glands to decrease the release of
parathyroid hormone?

Answer 7

Any condition that would increase the calcium ion concentration
in the extracellular fluid such as increased dietary consumption
of calcium, increased vitamin D consumption, or the increased
release of calcium from the bones from lack of use would
decrease the release of parathyroid hormone.
Guyton AC, & Hall, JE. Textbook of Medical Physiology. 12th
ed. Philadelphia: Saunders; 2011: 965.

Question 8

How do the parathyroid glands increase the

resorption of calcium and phosphate from the bone?

Answer 8

Parathyroid hormone increases bone resorption of calcium and
phosphate in two stages: the first stage begins within minutes
and increases the resorption activity of osteoclasts. The
second stage is much slower and may require several days or
weeks as it stimulates the increased production of osteoclasts.
Guyton AC, & Hall, JE. Textbook of Medical Physiology. 12th
ed. Philadelphia: Saunders; 2011: 963.

Question 9

How does parathyroid hormone act on the kidneys?

Answer 9

Parathyroid hormone can cause a rapid loss of phosphate ions
in the urine by its effect on the proximal tubule. As more
phosphate is excreted, calcium is retained. The increased
calcium reabsorption takes place primarily in the collecting
tubules and the late distal tubules.
Guyton AC, & Hall, JE. Textbook of Medical Physiology. 12th
ed. Philadelphia: Saunders; 2011: 964.

Question 10

What are the cardiac signs and symptoms of

hyperparathyroidism?

Answer 10

Hypertension, prolonged PR interval, and a shortened QT
interval.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 401.

Question 11

What are the neuromuscular signs and symptoms of

hyperparathyroidism?

Answer 11

Skeletal muscle weakness, bone demineralization, vertebral
collapse, and pathologic fractures.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 400-401.

Question 12

What are the renal signs and symptoms of

hyperparathyroidism?

Answer 12

Polyuria, polydipsia, decreased glomerular filtration rate,
hypophosphatemia, hyperchloremic acidosis and renal stones.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 400-401.

Question 13

What is the primary treatment of

hyperparathyroidism?

Answer 13

Besides the removal of the diseased portion of the parathyroid
glands, treatment of hyperparathyroidism is identical to the
treatment for symptomatic hypercalcemia. Saline infusion
(typically about 150 mL/hour) is the basic treatment, but the
effect of saline to lower calcium is limited and may require the
addition of loop diuretics which inhibit both sodium and calcium
reabsorption in the proximal loop of Henle. In the case of lifethreatening
hypercalcemia, bisphosphonates such as disodium
etidronate are the drugs of choice. Dialysis may also be used to
reduce calcium levels. Calcitonin administration may lower
calcium levels, but the effects of calcitonin are short-lived.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 400-401.

Question 14

What is secondary hyperparathyroidism?

Answer 14

Secondary hyperparathyroidism is defined as a normal,
compensatory increase in parathyroid hormone secretion in
response to a disease process or condition that produces
hypocalcemia, such as the increased parathyroid hormone
secretion associated with chronic renal disease. Because it is a
compensatory mechanism, it rarely produces hypercalcemia.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 402.

Question 15

What are the causes of primary hyperparathyroidism?

Answer 15

Primary hyperparathyroidism refers to the excessive secretion
of parathyroid hormone from a benign parathyroid tumor, a
cancerous parathyroid tumor, or parathyroid hyperplasia. 90%
of cases of primary hyperparathyroidism are due to a benign
tumor. Incidentally, hyperparathyroidism due to adenoma or
hyperplasia is most commonly associated with multiple
endocrine neoplasia.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 400.

Question 16

How is the care of the parturient with
hyperparathyroidism different from that of a
nonpregnant patient?

Answer 16

Maternal hypercalcemia can lead to fetal and newborn
hypocalcemia and is associated with increased neonatal
morbidity and mortality rates. Because the definitive treatment
for symptomatic hyperparathyroidism is removal of the
parathyroid glands, it is not unusual for a pregnant patient to
undergo this surgery.
Longnecker DE, Newman MF, Brown DL, Zapol WM.
Anesthesiology. 2nd ed. New York: McGraw-Hill; 2012: 154.

Question 17

How should you adjust your anesthetic for the patient

with primary hyperparathyroidism?

Answer 17

Your anesthetic should be aimed at dealing with underlying
hypercalcemia. Because of this, hydration with normal saline
and monitoring of urinary output is essential. Because
hypercalcemia is associated with somnolence, the anesthetic
requirement may be decreased. If personality changes due to
chronic hypercalcemia are present, then ketamine may need to
be avoided. Baseline skeletal weakness may necessitate a
decreased dose of nondepolarizing muscle relaxants, however
the increased calcium can antagonize muscle relaxants–in
short, hyperparathyroidism is associated with an increased
sensitivity to succinylcholine and a resistance to
nondepolarizing muscle relaxants. Acidosis increases the
serum calcium level, so hypoventilation should be avoided. As
with thyroidectomy, there is a risk of damage to the recurrent
laryngeal nerve during surgery, so a Nim(Registered) tube or
similar device should be used to monitor nerve function during
surgery. It is important to position patients with a risk of
pathologic fractures carefully.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 401-402.

Question 18

What are the signs and symptoms of

hypoparathyroidism?

Answer 18

The signs and symptoms of hypoparathyroidism depend on the
speed at which the hypocalcemia results. If it is acute, as in
inadvertent removal of the parathyroid glands during a
thyroidectomy, then the patient may complain of circumoral
paresthesias, agitation, and neuromuscular irritability (positive
Chvostek’s sign). Symptoms due to chronic hypocalcemia
include skeletal muscle weakness, prolonged QT interval,
calcification of the basal ganglia, and thickening of the skull.
The most common cause of chronic hypocalcemia is chronic
renal failure.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 402.

Question 19

What is the difference between hypoparathyroidism

and pseudohypoparathyroidism?

Answer 19

Hypoparathyroidism occurs when the secretion of parathyroid
hormone is decreased or absent or the tissues do not respond
to the released hormone. The most common cause of
decreased or absent parathyroid hormone is the removal of the
parathyroid glands during thyroidectomy.
Pseudohypoparathyroidism occurs when the hormone is
released normally, but the kidneys are unable to respond to the
hormone. Pseudohypoparathyroidism is associated with mental
retardation, basal ganglia calcification, obesity, decreased
height, and short metacarpals and metatarsal bones.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 402.

Question 20

hat is the treatment for hypoparathyroidism?

Answer 20

The treatment of hypoparathyroidism is aimed at restoring low
calcium levels to normal. An infusion of 10 mL of calcium
gluconate 10% IV should be administered until signs of
neuromuscular irritability resolve. Respiratory or metabolic
alkalosis should be normalized. Thiazide diuretics may be
helpful as they result in sodium depletion without the loss of
potassium which tends to increase calcium levels.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 402-403.

Question 21

What are the anesthetic considerations for the

patient with hypoparathyroidism?

Answer 21

The anesthetic implications are the same as those for a patient
with hypocalcemia. It is important to avoid hyperventilation as
the resulting alkalosis can decrease ionized calcium
concentrations. Administering whole blood with citrate does not
affect calcium concentrations because calcium can be
mobilized quickly into the bloodstream, however, the rapid
administration of blood can result in loss of ionized calcium.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 403.