7/29/2019 Parathyroid Adenoma With Renal Stones

1/1

Case: PARATHYROID ADENOMA WITH RENALSTONES

A 50-year old male entered theemergency room with right flank pain. The stonewas subsequently passed spontaneously andanalysis revealed it to be calcium oxalate. He hadnoted lethargy, polyuria, polydipsia, muscleweakness and diffuse bone pain.

Laboratory results showed plasma calciumof 12.3 mg/dl, phosphate of 1.9 mg/dl, creatinineof 1.5 mg/dl, and albumin of 5.9 g/dl. His plasmaalkaline phosphatase and urinary hydroxyprolinewere elevated. Urinary calcium excretion was 380mg/24 hours. After water deprivation, urineosmolality did not exceed 290 mOsm/kg.

A single, very large parathyroid gland wassurgically removed from the patients neck. Hisserum calcium level decreased to 6 mg/dl.

Notes:Parathyroid Gland, located at the neck, is

responsible for the production of ParathyroidHormone (PTH) which regulates the level ofcalcium and phosphate in the blood and bone.Parathyroid Hormone is produced by the chiefcell. Parathyroid Adenoma is a noncancerous(benign) tumor of the parathyroid glands.

LEARNING OBJECTIVES:1. Identify the most likely hormonal causes

of hypercalcemia in this case.

Increased production of ParathyroidHormone (PTH) or Hyperparathyroidism

due to parathyroid adenoma causes theincrease amount of Calcium in the body.

2. Discuss the mechanism for hypercalcemiainduced by the different hormonal causes

Parathyroid Hormone(PTH) controls thelevel of calcium in the blood and bone.Hyperparathyroidism or increased

production of Parathyroid Hormone willcause an increase in plasma Ca+ by- stimulating bone resorption

- increasing Ca+ reabsorption of thekidneys

- stimulating the production of calcitriol

3. Compare the effect of parathyroidhormone and vitamin D on plasmaphosphate level

-PTH increases amount of Calcium butdecreases the amount of Phosphate.-Vitamin D or Calcitriol increases theamount of Calcium as well as the amountof Phosphate

4. Explain the mechanism for the followinga. Renal stones

In the kidneys Ca is reabsorbed in theDistal Tubule. Hyperparathyroidismincreases the amount of Ca, thus theincrease in the amount of Ca willexceed the renal threshold forreabsorption of Calcium and it will

precipitate causing renal stones.

Bone pain

Because of the hypersecretion of PTH, it will

activate osteoclast and increase bone

resorption, this increase of PTH creates

microfissures in bones where blood and

other impurities tend to collate.Thisstimulates the nociceptors in the bones

which signals pain.

c. Polyuria

Hypercalcemia inhibits ADH thuscausing polyuria. It disrupts the osmoticgradient in the tubules and also thereceptor sites of ADH.

d. Elevated alkaline phosphate

Alkaline phosphatase is an enzyme thatliberates phosphate from bones or the liver.The increase in Alkaline Phosphate is due to

increased bone resorption due to high levelsof PTH.

e. Elevated urinary hydroxyproline

One of the main components of bone iscollagen and it containes appreciablequantities of hydroxyprolone. And dueto bone resorption, there is adestruction of the organic matrix of thebone (collagen), which will be excretedin the urine.

5. Discuss the two mechanisms for thereduction of serum calcium after surgery

1. In the bone, removal of the adenomawill cause bone resorption to stop.Calcium will be reabsorbed back into thebone thus decreasing the amount of theserum calcium.2. In the kidneys, removal of the adenomawill cause a decrease in Ca excretion thuslowering the amount of serum calcium