Hyperparathyroidism
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Hyperparathyroidism
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USMLE® Step 1 style questions USMLE
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Routine blood work is performed. Which of the following sets of findings will most likely be seen in this patient?
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Abdominal pain
hyperparathyroidism p. 342
Acute pancreatitis p. 404
hyperparathyroidism p. 342
Alkaline phosphatase (ALP) p. 397, 468
hyperparathyroidism and p. 342
cAMP (cyclic adenosine monophosphate)
hyperparathyroidism p. 342
Depression
hyperparathyroidism p. 342
Hypercalcemia p. 609
hyperparathyroidism p. 342
Hypercalciuria
hyperparathyroidism p. 342
Hyperparathyroidism p. 342
associations p. 732
calcium pyrophosphate deposition disease p. 473
cinacalcet for p. 361
lab findings p. 728
lab values in p. 467
osteoporosis p. 467
renal osteodystrophy and p. 622
Hyperphosphatemia p. 609
hyperparathyroidism (secondary) p. 342
Hypocalcemia p. 335, 609
hyperparathyroidism p. 342
Hypophosphatemia p. 609
hyperparathyroidism p. 342
Kidney stones p. 620
hyperparathyroidism p. 342
Pancreatitis p. 404
hyperparathyroidism as cause p. 342
Parathyroid adenomas
hyperparathyroidism caused by p. 342
Parathyroid hormone (PTH) p. 334
in hyperparathyroidism p. 342
Polyuria p. 618
hyperparathyroidism p. 342
Tertiary hyperparathyroidism p. 342
Vitamin D deficiency p. 348
hyperparathyroidism p. 469
Transcript
Content Reviewers
With hyperparathyroidism, “hyper” refers to over, and “parathyroid” refers to the parathyroid glands, so hyperparathyroidism refers to a condition where there is an overproduction of parathyroid hormone.
Parathyroid hormone comes from the parathyroid glands which are buried within the thyroid gland, and their main job is to keep blood calcium levels stable.
Now, the majority of the extracellular calcium, the calcium in the blood and interstitium, is split almost equally between two groups - calcium that is diffusible and calcium that is not diffusible.
Diffusible calcium is small enough to diffuse across cell membranes and is separated into two subcategories.
The first is free-ionized calcium, which is involved in all sorts of cellular processes like neuronal action potentials, contraction of skeletal, smooth, and cardiac muscle, hormone secretion, and blood coagulation, all of which are tightly regulated by enzymes and hormones.
The second category is complexed calcium, which is where the positively charged calcium is ionically linked to tiny negatively charged molecules like oxalate, which is a small anion that are normally found in our blood in small amounts.
The complexed calcium forms a molecule that’s electrically neutral but unlike free-ionized calcium it’s not useful for cellular processes.
Both of these are called diffusible because they’re small enough to diffuse across cell membranes.
Finally there’s the non-diffusible calcium which is bound to negatively charged proteins like albumin.
The resulting protein-calcium complex is too large and charged to cross membranes, leaving this calcium also uninvolved in cellular processes.
Changes in the body’s levels of extracellular calcium are detected by a surface receptor in parathyroid cells that’s called the calcium-sensing receptor.
These changes affect the amount of parathyroid hormone that’s released by the parathyroid gland.
The parathyroid hormone gets the bones to release calcium, it gets the kidneys to reabsorb more calcium so it's not lost in the urine, and it synthesizes calcitriol, which is also known as 1,25-dihydroxycholecalciferol, or active vitamin D.
Summary
Hyperparathyroidism is a condition in which the parathyroid glands produce too much parathyroid hormone (PTH), which regulates calcium levels in the blood. Hyperparathyroidism can be primary, secondary, or even tertiary.
Primary hyperparathyroidism usually results from PTH secretion by a parathyroid adenoma. It is characterized by excess PTH that leads to high blood calcium levels (hypercalcemia), bone mass loss, kidney stones, and other health problems, such as psychiatric issues.
Secondary hyperparathyroidism develops when there are conditions like chronic kidney disease, which can lead to low calcium, high phosphate, and low vitamin D levels. It is mainly characterized by osteodystrophy, in which there is bone weakening associated with bone pain and deformation.
Finally, there is tertiary hyperparathyroidism, which occurs because of chronic secondary hyperparathyroidism from kidney disease. This leads to hypercalcemia and phosphate imbalances.
Sources
- "Robbins Basic Pathology" Elsevier (2017)
- "Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2)" McGraw-Hill Education / Medical (2018)
- "Pathophysiology of Disease: An Introduction to Clinical Medicine 8E" McGraw-Hill Education / Medical (2018)
- "CURRENT Medical Diagnosis and Treatment 2020" McGraw-Hill Education / Medical (2019)
- "Harrison's Endocrinology, 4E" McGraw-Hill Education / Medical (2016)
- "Vitamin D Deficiency and Secondary Hyperparathyroidism in the Elderly: Consequences for Bone Loss and Fractures and Therapeutic Implications" Endocrine Reviews (2001)
- "Calcimimetics for secondary hyperparathyroidism in chronic kidney disease patients" Cochrane Database of Systematic Reviews (2014)