Download MBBS (Bachelor of Medicine, Bachelor of Surgery) General Surgery PPT 7 Parathyroid Gland Lecture Notes
PARATHYROID GLAND
Anatomy and Embryology
.4 parathyroid glands situated posterior to the thyroid.
.Superior glands:
Found just superior to the intersection of the inferior thyroid artery and the recurrent
laryngeal nerve.
Derived from the fourth pharyngeal pouch.
Occasional y found within the substance of the thyroid gland.
.Inferior glands
Derived from the third pharyngeal pouch.
Embryologic association with the thymus, the inferior glands are often found adjacent to or
within the thymus.
Usual y located near the inferior pole of the thyroid.
Physiology
.Parathyroid Hormone:
Primarily responsible for maintaining extracel ular calcium concentrations.
Secretion is regulated directly by the plasma conc. of ionized calcium.
.Effects of parathyroid hormone
Increase the concentration of plasma calcium by-
o Increasing the release of calcium and phosphate from bone matrix.
o Increasing calcium reabsorption by the kidney.
o And increasing renal production of 1,25-dihydroxyvitamin D-3 (calcitriol), which increases
intestinal absorption of calcium.
Also causes phosphaturia, thereby decreasing serum phosphate levels.
Primary Hyperparathyroidism
.Unregulated overproduction of parathyroid hormone (PTH) resulting in
abnormal calcium homeostasis.
.Etiology:
Hyperplasia Or Adenoma
85% of cases- a single adenoma.
15% of cases- multiple glands are involved (ie, either multiple adenomas or hyperplasia)
Rarely- parathyroid carcinoma.
Primary Hyperparathyroidism
.Most cases- sporadic.
.Familial cases can occur either as part of-
Multiple endocrine neoplasia syndromes (MEN 1 or MEN 2a).
Hyperparathyroid-jaw tumor (HPT-JT) syndrome.
Familial isolated hyperparathyroidism (FIHPT).
Pathophysiology
.In primary hyperparathyroidism
Adenomas- the normal feedback on parathyroid hormone production by
extracel ular calcium seems to be lost.
In parathyroid hyperplasia- an increase in the cel numbers is probably the
cause.
.The chronic excessive resorption of calcium from bone-
Result in osteopenia/ osteoporosis.
Pathophysiology....
.In severe cases-
May result in Osteitis Fibrosa Cystica.
Subperiosteal resorption of the distal phalanges.
Tapering of the distal clavicles.
Salt-and-pepper appearance of the skul .
And brown tumors of the long bones.
The chronical y increased excretion of calcium in the urine-
Can predispose to the formation of renal stones.
Pathophysiology....
.Other symptoms due to the hypercalcemia itself-
Muscle weakness, fatigue.
Volume depletion, nausea and vomiting.
And in severe cases- coma and death.
Neuropsychiatric manifestations are particularly common and may include
depression.
Can increase gastric acid secretion-
o may have a higher prevalence of peptic ulcer disease.
Pancreatitis.
Symptoms
.The clinical syndrome of primary hyperparathyroidism:
"Bones, stones, abdominal groans, and psychic moans."
.Skeletal manifestations include-
Bone and joint pain, pseudogout, and chondrocalcinosis.
Osteitis fibrosa cystica.
.Renal manifestations include-
Polyuria, kidney stones, hypercalciuria and rarely nephrocalcinosis.
Symptoms....
.Gastrointestinal manifestations include-
Anorexia, nausea, vomiting.
Abdominal pain, constipation, peptic ulcer disease.
And acute pancreatitis.
.Neuromuscular and psychologic manifestations include-
Proximal myopathy, weakness and easy fatigability.
Depression, inability to concentrate, and memory problems.
.Cardiovascular manifestations include-
Hypertension, bradycardia, and left ventricular hypertrophy
Examination
.Physical examination findings- usually noncontributory.
.Examination may reveal- muscle weakness and depression.
.A palpable neck mass-
not usual y expected with hyperparathyroidism
in rare cases, it may indicate parathyroid cancer.
Workup
Blood
.Total serum calcium and albumin levels or ionized calcium levels.
Hypercalcemia should be documented on more than one occasion before a
diagnostic workup is undertaken.
.An elevated intact parathyroid hormone level with an elevated ionized
serum calcium level-
Diagnostic of primary hyperparathyroidism.
.A 24-hour urine calcium measurement- is necessary to rule out FHH.
.Mild hyperchloremic acidosis, hypophosphatemia, and mild-to-moderate
increase in urinary calcium excretion rate.
Imaging
.Imaging studies are used to guide the surgeon once surgical
therapy has been decided.
.Nuclear medicine scanning with Radiolabeled Sestamibi-
A widely used technique.
Radionuclide concentrated in thyroid and parathyroid tissue-
Usually washes out of normal thyroid tissue in under an hour.
Persists in abnormal parathyroid tissue.
Therefore, on delayed images, an abnormal parathyroid is seen as a persistent focus
of activity.
Imaging....
.Ultrasonography of the neck-
May be equivalent or superior to sestamibi scanning.
.CT scanning and MRI-
Now been largely replaced by sestamibi scanning and ultrasound.
.Dual-energy X-ray absorptiometry (DXA)-
A useful tool to demonstrate the skeletal involvement in primary
hyperparathyroidism.
Treatment
Hypercalcemic Crisis
.Intravascular volume expansion with sodium chloride.
.Loop diuretics such as furosemide once the intravascular volume is
restored.
.Drugs such as calcitonin and IV bisphosphonate have been used as a
temporary measure prior to surgical treatment.
Medical Treatment
.Monitoring:
Patients who do not meet the guidelines for surgical intervention can be
monitored safely.
.Annual assessment:
For overt signs and symptoms of primary hyperparathyroidism.
Serum creatinine level
And 3-site dual-energy x-ray absorptiometry (DXA) study.
.Serum calcium should be checked every 6 months.
Medical Treatment....
.Diet and lifestyle:
Patients should maintain a moderate daily elemental calcium intake of
800-1000 mg and a vitamin D intake appropriate for their age and sex.
Maintaining good hydration.
Participation in regular exercise activity.
And avoidance of certain medications (such as thiazides, diuretics, and
lithium) are desirable.
Medical Treatment....
.Pharmacotherapy:
Estrogen therapy.
Selective estrogen receptor modulators-
such as raloxifene.
Bisphosphonates-
Alendronate.
Calcimimetic drugs-
such as cinacalcet.
Medical Treatment....
.Other treatments:
Percutaneous alcohol injection and other percutaneous ablation techniques
Have been suggested as an alternative treatment in patients who
cannot or wil not undergo surgery.
Percutaneous techniques have high complication rates in smal
numbers of patients
Their routine use cannot yet be supported.
Surgery
.Indications for surgery-
1.0 mg/dL above the upper limit of the reference range for serum
calcium.
24-hour urinary calcium excretion greater than 400 mg.
A 30% reduction in creatinine clearance.
Bone mineral density T-score below -2.5 at any site.
Age younger than 50 years.
Surgery....
.Standard operative approach:
Complete neck exploration with identification of al parathyroid glands.
OR
Removal of al abnormal glands with autotransplantation.
In the case of 4-gland hyperplasia-
3.5-gland parathyroidectomy is performed.
A nonabsorbable suture is left as a tag to identify the gland.
Secondry
Hyperparathyroidism
Secondry
Hyperparathyroidism
.Secondary hyperparathyroidism:
Overproduction of parathyroid hormone
Secondary to a chronic abnormal stimulus for its production.
.Typically, this is due to chronic renal failure.
.Another common cause is vitamin D deficiency.
Etiology
.In chronic kidney disease-
Overproduction of parathyroid hormone occurs in response to
hyperphosphatemia, hypocalcemia.
And impaired 1,25-dihydroxyvitamin D production by the diseased kidneys.
.Hyperphosphatemia-
Directly stimulate parathyroid hormone synthesis and parathyroid
hyperplasia.
And indirectly promotes secondary hyperparathyroidism by decreasing free
calcium level.
Clinical Features
.Virtually all patients with renal failure have
Hyperparathyroidism to some degree
Clinical presentation is often that of renal failure.
.In secondary hyperparathyroidism due to vitamin D deficiency
Symptoms are mainly due to the vitamin deficiency
E.g.- osteomalacia with increased fracture risk, myopathy.
.In advanced cases- some patients may have bone pain.
Workup
.Serum level of parathyroid hormone, calcium, phosphorus, and 25-
hydroxyvitamin D should be measured.
.Patients with secondary hyperparathyroidism usually have
A low-normal calcium and elevated parathyroid hormone.
.The phosphate level may vary based on the etiology-
High values in renal insufficiency
And low values in vitamin D deficiency.
Treatment
.Medical management is the mainstay of treatment for secondary
hyperparathyroidism.
.Correcting vitamin D deficiency can be achieved using-
50,000-IU capsule of vitamin D-2 once a week for 8 weeks
and repeating the course for another 8 weeks if needed to achieve vitamin D
sufficiency.
Treatment
.Current nonsurgical treatment options for management of secondary
hyperparathyroidism in chronic kidney disease:
Dietary phosphate restriction .
Phosphate binders can be used if hyperphosphatemia persists despite dietary
phosphate restriction.
Calcium-based phosphate binders such as calcium carbonate or calcium acetate
Non-calcium-based phosphate binders such as sevelamer hydrochloride or lanthanum carbonate
Calcium supplementation should be limited to less than 2 g/d.
Vitamin D and its analogs.
Treatment with calcimimetics such as cinacalcet.
Treatment
.Indications for surgery include-
Bone pain or fracture
Pruritus, calciphylaxis
And extraskeletal nonvascular calcifications with elevated PTH levels
despite appropriate medical therapy.
Tertiary
Hyperparathyroidism
Tertiary Hyperparathyroidism
.Tertiary disease is characterized by-
Development of autonomous hypersecretion of parathyroid hormone causing
hypercalcemia.
.Etiology is unknown.
. but may be due to monoclonal expansion of parathyroid cells (nodule formation
within hyperplastic glands).
. A change may occur in the set point of the calcium-sensing mechanism to
hypercalcemic levels.
. Four-gland involvement occurs in most patients.
PATHOPHYSIOLOGY
Observed most commonly in-
Patients with chronic secondary hyperparathyroidism and often after renal
transplantation.
Hypertrophied parathyroid glands fail to return to normal-
Continue to over secrete parathyroid hormone, despite serum calcium levels that
are within the reference range or even elevated.
Hypertrophied glands become autonomic and cause hypercalcemia, even after
withdrawal of calcium and calcitriol therapy.
This type of tertiary disease is particularly dangerous because the
phosphate level is often elevated.
TREATMENT
.Total parathyroidectomy with autotransplantation
.Subtotal parathyroidectomy.
This post was last modified on 07 April 2022