Endocrine pathology Flashcards
What is a pituitary adenoma? What are the common types?
A pituitary adenoma is a benign tumor of anterior pituitary cells.
Nonfunctional pituitary adenoma (does not produce hormones)
Prolactinoma
Growth hormone cell adenoma
ACTH cell adenoma
(TSH cell, LH-producing and FSH-producing adenomas are very rare)
How do nonfunctional pituitary adenomas present?
Present with mass effect. Since the pituitary sits in the sella turcica, growth of the pituitary causes:
bitemporal hemianopsia (blindness in outer visual fields) due to compression of the optic chiasm
hypopituitarism
headache
What are the manifestations of a prolactinoma? How would you treat a prolactinoma?
Prolactin causes milk production and inhibits release of GnRH
In females - galactorrhea and amenorrhea
in males - decreased libido and headache
Treatment is with dopamine agonists (e.g. bromocriptine) because dopamine suppresses prolactin release
What are the manifestations of a growth hormone cell adenoma? in children? In adults? How id GH cell adenoma treated?
In children - gigantism (increased linear bone growth)
In adults - acromegaly (enlarged bones of hands, feet and jaw, growth of visceral organs, enlarged tongue)
Secondary diabetes b/c GH induces liver gluconeogenesis
Treatment is octreotride, a somatostatin (growth hormone inhibiting hormone) analog that suppresses GH release, or GH receptor antagonists
What are the causes of hypopituitarism?
pituitary adenomas, craniopharyngioma (children) growth compresses the pituitary.
Sheehan syndrome - excessive blood loss during birth causes infarction of pituitary gland. Pituitary gland is susceptible to infarction during pregnancy b/c the gland doubles in size but the blood supply does not increase as much. Presents as poor lactation and loss of pubic hair
What is the pathogenesis of central diabetes insipidus? What are the clinical features? What is the treatment?
An ADH deficiency due to hypothalamic or posterior pituitary pathology (e.g. tumor, trauma, infection or inflammation)
Clinical features: (losing free water in urine)
polyuria and polydipsia
hypernatremia and high serum osmolarity
low urine osmolality and specific gravity
Treatment is desmopressin, an ADH analog
What is nephrogenic diabetes insipid us?
ADH levels are normal, but the kidney does not respond to the hormone. Due to inherited mutations or drugs (e.g. demeclocycline).
Cannot treat with desmopressin.
What is the pathogenesis of SIADH? What are the clinical features?
Syndrome of inappropriate ADH is marked by excessive ADH secretion due to ectopic production (e.g. small cell carcinoma of the lung)
Clinical features: (body retains too much water)
Hyponatremia and low serum osmolality leads to neuronal swelling and cerebral edema which leads to mental status changes and seizures
What are the three layers of the adrenal cortex and what does each layer secrete?
Glomerulosa - aldosterone (mineralocorticoids)
Fasiculata - cortisol (glucocorticoids)
Reticularis - sex steroids
What is Cushing syndrome? What 4 things can cause it? How can you distinguish between these causes?
When the body makes excess cortisol.
Causes:
exogenous corticosteroids lead to bilateral adrenal atrophy
primary adrenal adenoma, hyperplasia or carcinoma leads to atrophy of the uninvolved adrenal gland
ACTH secreting pituitary adenoma leads to bilateral adrenal hyperplasia
paraneoplastic ACTH secretion leads to bilateral adrenal hyperplasia
To distinguish between the ACTH secreting adenoma and paraneoplastic ACTH secretion, you can use high-dose dexamethasone (cortisol analog) to suppress ACTH production by an adenoma but fails to suppress neoplastic ACTH production
What are the clinical features of Cushing syndrome?
Muscle weakness and thin extremities (cortisol breaks down muscle protein for gluconeogenesis)
Moon facies, buffalo hump, truncal obesity (high glucose causes high insulin which increases storage of fat)
Abdominal striae (cortisol impairs collagen synthesis and causes thinning of the skin)
Hypertension
Osteoporosis
Immune suppression
What types of cells does aldosterone act upon? What does it do? How would hyperaldosteronism present? Hypoaldosteronism?
Acts on the principle cells and alpha-intercalated cells in the late distal tubule and collecting duct.
Increases resorption of sodium
Dumps potassium
Dumps H+
Hyperaldosteronism - hypernatremia (and hypertension), hypokalemia and metabolic alkalosis
Hypoaldosteronism - hyponatremia (and hypotension), hyperkalemia and metabolic acidosis
What are the causes of primary hyperaldosteronism? What are the laboratory findings? What are the causes of secondary hyperaldosteronism? What are the laboratory findings?
Mostly caused by an adrenal adenoma. Sporadic hyperplasia and carcinoma are rare causes.
Lab findings: high aldosterone (secreted by adenoma) and low renin (hypertension causes negative feedback on the RAS)
Causes of secondary hyperaldosteronism: activation of renin-angiotensin system from fibromuscular dysplasia of renal artery, atherosclerosis of renal artery, any stenosis of renal artery
Lab findings: high aldosterone and high renin
What is the most common enzyme deficiency that causes congenital adrenal hyperplasia? What are other enzyme deficiencies that can cause CAH? How can you distinguish between them?
21 hydroxylase deficiency is the most common cause of CAH
11 hydroxylase deficiency can also cause CAH
21H deficiency is characterized by no mineralocorticoids nor cortisol. 11H deficiency is characterized by no cortisol but a little bit of mineralocorticoids.
What is the pathogenesis of congenital adrenal hyperplasia? What are the clinical manifestations of CAH?
A deficiency in one of the enzymes in the steroid pathway blocks production of mineralocorticoids and cortisol, shunting all the steroid precursors (pregnenolone) down the sex steroid pathway.
Clinical manifestations of:
Increased sex steroids - clitoral enlargement in females, precocious puberty in males
Lack of cortisol - hypotension, increased ACTH secretion -> bilateral adrenal hyperplasia
Lack of mineralocorticoids - hyponatremia, hyperkalemia, hypovolemia
