Parathyroid Pathology (Hillard) Flashcards by Takara Newsome

embryology of parathyroid gland

superior parathyroid - 4th pharyngeal pouch
inferior parathyroid - 3rd pharyngeal pouch

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Chief cells

produce parathyroid hormone (PTH)

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CaSR mechanism

Calcium-sensing receptor (Gi) present on parathyroid chief cells; binds calcium and inhibits PTH release

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What are the 3 possible causes of primary hyperparathyroidism?

Parathyroid adenoma (95%)
Parathyroid hyperplasia (5%)
Parathyroid carcinoma (rare)

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Parathyroid adenoma

benign; typically affects a single gland; 1/3 are due to sporadic MEN 1 mutations

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Parathyroid hyperplasia

enlargement of all 4 glands

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Parathyroid carcinoma

malignant; usually large; features of malignancy:
vascular invasion
invasion of adjacent structures/organs
metastasis

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Clinical presentation of primary hyperparathyroidism

usually asymptomatic and picked up by routine calcium screening; when symptomatic “Bones, Stones, Abd Groans and Psychic Moans”

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Hyperparathyroidism effects on bone

osteoporosis
Osteitis fibrosis cystica - cystic brown tumors, bone cysts

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Parathyroid disease work-up

imaging studies; sestamibi scintigraphy and SPECT -single photon emission computed tomography

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What is the most reliable feature to distinguish parathyroid adenoma vs hyperplasia

number of glands involved
adenoma: one gland
hyperplasia: all 4 are involved

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Treatment of parathyroid adenoma and hyperplasia

surgical resection for both
adenoma excision and 3 1/2 glands removed in hyperplasia (if de-vascularized put remaining 1/2 in forearm)

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Most common cause of secondary hyperparathyroidism

renal failure; decreased production of calcitriol; decreased phosphate excretion (HYPERphosphatemia) binding to free Ca2+; resulting in hypocalcemia

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secondary hyperparathyroidism

prolonged hypocalcemia causes compensatory PTH release; expect to see parathyroid hyperplasia

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Secondary hyperparathyroidism of renal failure

Renal osteodystrophy - bone pain and fractures
Calciphylaxis - vessel calcifications causing vascular compromise, necrosis of skin; associated w/ HYPERphosphatemia

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Calciphylaxis

seen in secondary hyperparathyroidism of renal failure; vessel calcifications causing vascular compromise, necrosis of skin; associated w/ HYPERphosphatemia

Tertiary hyperparathyroidism

persistent secretion of PTH after long-standing secondary hyperparathyroidism; usually due to chronic renal failure or end-stage renal disease

Hypercalcemia of malignancy

tumor secretion of PTH-related peptide (PTHrP); neoplastic phenomenom

Hypercalcemia in sarcoidosis

non-caseating granulomatous disease; bilateral hilar lymphadenopathy; hypercalcemia caused by increased 1-alpha hydroxylase in macrophages creates calcitriol (activated Vit. D)

Cause of hypercalcemia in sarcoidosis

increased 1-alpha hydroxylase in macrophages creates calcitriol (activated Vit. D)

Major causes of hypoparathyroidism

Acquired: surgical mistake or autoimmune APS-1 mut
Congenital: DiGeorge, AD hypoparathyroidism or familial isolated hypoparathyroidism

**both PTH and Ca2+ are low

Chvostek sign

finding in hypoparathyroidism; tapping of facial nerve causes contraction of muscles

Trousseau sign

finding in hypoparathyroidism; carpal spasm w/ occlusion of arm w/ BP cuff

Findings in hypocalcemia

Tetany - paresthesias, spasms and seizures
Chvostek sign
Trousseau sign

DiGeorge Syndrome

CATCH-22 deletion of chr 22q11 pharyngeal pouch development issue, underdeveloped parathyroid gland, decreased PTH, decreased Ca2+

Autosomal Dominant hypoparathyroidism

GOF mut in CASR gene; increase sensitivity to Ca2+; PTH is inhibited; low PTH and low Ca2+

Pseudohypoparathyroidism

presents in childhood, end-organ resistance to PTH due to mutation in G protein receptor; low Ca2+ despite elevated PTH; resistance to other anterior pituitary hormones as well; Albright Hereditary Osteodystrophy

Albright Hereditary Osteodystrophy

Pseudohypoparathyroidism; presents in childhood, end-organ resistance to PTH due to mutation in G protein receptor; low Ca2+ despite elevated PTH; resistance to other anterior pituitary hormones as well

MEN 1

"PPP" Pituitary adenoma Parathyroid adenoma/hyperplasia Pancreatic endocrine tumors and duodenal gastrinoma

MEN 2A

"PM Pheo" Parathyroid hyperplasia Medullary thyroid carcinoma Pheochromocytoma

MEN 2B

"MMM Pheo"; germline missense mut in RET Mucosal neuromas Marfanoid body Medullary thyroid carcinoma Pheochromocytoma **no involvement with parathyroid unlike MEN2A

MEN 4

Pituitary and parathyroid (similar to MEN 1)

Wermer syndrome

MEN 1 (tumor suppressor) mut; "PPP" Pituitary adenoma - PRL (galactorrhea and amenorrhea) Parathyroid adenoma/hyperplasia (bones, stones, abd groans and psychiatric moans" Pancreatic endocrine tumors - insulinoma (hypoglycemia) and duodenal gastrinoma - Zollinger-Ellison syndrome

Zollinger-Ellison syndrome is associated with which MEN disorder?

MEN 1 AKA Wermer syndrome; "PPP" Pituitary adenoma Parathyroid adenoma/hyperplasia Pancreatic endocrine tumors and duodenal gastrinoma

Testing for suspected MEN 1

DNA testing

Sipple Syndrome

MEN 2A; GOF RET proto-oncogene; "PM Pheo" Parathyroid hyperplasia Medullary thyroid carcinoma - C cell hyperplasia (calcitonin) Pheochromocytoma

Gain of function RET proto-oncogene is seen in which MEN disorder?

Sipple Syndrome; MEN 2A; "PM Pheo" Parathyroid hyperplasia Medullary thyroid carcinoma - C cell hyperplasia (calcitonin) Pheochromocytoma

Germline missense mut in RET is seen in which MET disorder?

MEN 2B; "MMM Pheo"; Mucosal neuromas Marfanoid body Medullary thyroid carcinoma Pheochromocytoma **no involvement with parathyroid unlike MEN2A