Endocrinology Flashcards
What is the most common pituitary adenoma?
Prolactinoma
Why does prolactinoma cause decreased libido in men and amenorrhea in females?
Because prolactin inhibits the release of GnRH
Why does GH adenoma cause DM II?
Because GH decreases glucose uptake into cells
What is pituitary apoplexy?
Bleeding into a pituitary adenoma
Sheehan syndrome
Pituitary gland doubles in size during pregnancy but its blood supply doesn’t increase. During childbirth, if the mother loses a lot of blood, the pituitary can be susceptible to ischemia. Presents as failure to lactate and loss of pubic hair
How does Sheehan syndrome present?
Failure to lactate and loss of pubic hair.
What causes empty sella syndrome?
Herniation of arachnoid/CSF into the sella causing destruction of the pituitary.
What is seen on water deprivation test in central diabetes insipidus?
Water deprivation fails to increase urine osmolality
Anterior cystic midline neck mass that moves with swallowing
Thyroglossal duct cyst
Most common site of ectopic thyroid tissue
Tongue
How does thyroid hormone increase BMR?
Increases Na/K ATPase
How does thyroid hormone increase HR?
Increases beta-1 receptors
What does excess thyroid hormone do to cholesterol and glucose levels?
Hypocholesterolemia. Hyperglycemia (increased gluconeogenesis/glycogenolysis).
What causes exophthalmos and pretibial myxedema in Graves’ disease?
Fibroblasts in eye and on the shin have TSH receptors, and secrete excess glycosaminoglycans in response to excess TSH.
Scalloping of colloid
Graves’ disease
What is myxedema?
Hypothyroidism - causes weight gain, enlarged tongue, deepening of voice (laryngeal edema), muscle weakness, cold intolerance.
Genetic association with Hashimoto thyroidtis
HLA-DR5
1 cause of thyroiditis where iodine levels are sufficient
Hashimoto - hyperthyroidism that progresses to hypothyroidism
2 antibodies seen in Hashimoto thyroiditis
Antithyroglobulin and antimicrosomal antibodies
Antimicrosomal antibodies
Hashimoto thyroiditis
Antithyroglobulin antibodies
Hashimoto thyroiditis
Formation of germinal centers of the thyroid
Hashimoto thyroiditis
What are Hurthle cells?
Intensely eosinophilic metaplasia seen in Hashimoto thyroiditis
Histology of Hashimoto thyroiditis
Chronic inflammation with formation of germinal centers and Hurthle cells (intensely eosinophilic metaplasia)
Granulomatous thyroiditis following a viral infection
Subacute (deQuervain’s) Granulomatous thyroiditis. Thyroid will be very tender, pain “marches” across thyroid.
Very tender thyroid with pain marching across it
Subacute (deQuervain’s) Granulomatous thyroiditis.
Hard as wood thyroiditis
Reidel fibrosing thyroiditis
Describe the findings in Subacute (deQuervain’s) Granulomatous thyroiditis
Granulomatous thyroiditis following a viral infection. Thyroid will be very tender, and pain will “march” across thyroid.
Describe the findigns in Reidel fibrosing thyroiditis
Hard as wood thyroid - nontender
Young patient with hard as wood thyroid and dyspnea. What happened?
Fibrosis from Reidel fibrosing thyroiditis has locally invaded the airway. Seen in YOUNG patients (vs. anaplastic carcinoma which does the same thing in OLD patients).
Describe the findings in iodine uptake studies in Graves disease
Increased
Describe the findings in iodine uptake studies in nodular goiter
Increased
Describe the findings in iodine uptake studies in cancer
Decreased (cold)
How do you biopsy the thyroid?
Fine needle aspiration (biopsy will cause it to bleed like crazy).
What is the hallmark of follicular adenoma of the thyroid?
Cells surrounded by a fibrous capsule - does not invade capsule!
What are the 4 types of thyroid cancer?
Papillary- psammoma bodies, increased risk with irradiation. Orphan Annie eye nuclei, nuclear grooves. Spreads to cervical nodes. Excellent prognosis. Follicular - encapsulated, but invades through capsule (FNA can’t tell it from follicular adenoma). Spreads hematogenously. Anaplastic -seen in older people. Invades locally (can cause dysphagia). Poor prognosis. Spindle cells. Medullary- MEN 2A, 2B, RET oncogene mutation. Malignant cells in an amyloid stroma. Calcitonin is a marker.
1 risk factor for development of papillary thyroid CA
Radiation
Bx of a thyroid mass shows nuclei with a central white clearing
Papillary carcinoma of the thyroid (orphan Annie eyes)
Bx of a thyroid mass shows nuclei with nuclear grooves
Papillary carcinoma of the thyroid
How does papillary CA of the thyroid spread?
Lymphatics (cervical nodes)
Orphan Annie eyes nuclei
Papillary carcinoma of the thyroid
Bx of a thyroid mass shows psammoma bodies
Papillary carcinoma of the thyroid
What distinguishes a follicular adenoma from a follicular carcinoma of the thyroid?
Both are surrounded by a capsule. Follicular carcinoma invades through the capsule, adenoma is contained within the capsule
Why is FNA limited in diagnosis of follicular CA of the thyroid?
Because you need to see the tumor invading through the capsule to call it carcinoma. Adenoma is surrounded by a capsule but it doesn’t invade it.
How does follicular CA of the thyroid spread?
Hematogenously (other carcinomas spreading through blood: RCC, HCC, choriocarcinoma)
Medullary CA is a neoplastic proliferation of…
C cells (why you use calcitonin as marker)
What is a marker for medullary CA of thyroid?
Calcitoninnnnnnnnnnnnjnnkscsnkncnnnnnnnnnnasdcleeesadccmxxxxxleopeorplllodadflloldafdscdmcamdckdnwaddddeededddded
What deposits as localized amyloid in medullary thyroid CA?
Calcitonin
Malignant thyroid tumor cells in an amyloid stroma.
Medullary thyroid CA
Medullary thyroid CA is associated with what 2 genetic conditions?
MEN 2A, 2B (deletion of RET oncogene)
What oncogene is deleted in MEN 2A and 2B?
RET oncogene
RET oncogene mutation
Familial medullary CA of the thyroid - MEN 2A, 2B
Patient has RET oncogene mutation. What procedure should they undergo?
Prophylactic thyroidectomy to reduce the chance of medullary thyroid CA.
Thyroid CA that invades locally
Anaplastic (seen in older people vs. Reidel thyroiditis that occurs in young people)
Thyroid biopsy shows spindle cells
Anaplastic CA - very poor prognosis.
Explain the MOA of parathyroid hormone on bone
Activates osteoblasts, which activate osteoclasts to break down bone
How does increased PTH cause acute pancreatitis?
High calcium is an enzyme activator
Why does alkaline phosphatase increase with increases in PTH?
Because osteoblasts are turned on by PTH, producing alkaline phosphatase. Osteoblasts then activate osteoclasts.
What is the #1 cause of secondary hypoparathyroidism?
Renal failure - decreased vitamin D = decreased calcium = increased PTH.
What causes pseudohypoparathyroidism?
Kidney resistance to PTH - defect in Gs protein.
Patient has hypocalcemia, increased PTH levels, short 4th and 5th digits. Dx?
Pseudohypoparathyroidism - Albright’s hereditary osteodystrophy. Autosomal dominant.
What is Chvostek’s sign? What causes it?
Tapping of facial nerve causing contraction of muscles - caused by hypocalcemia (hypoparathyroidism).
What is Trousseau’s sign? What causes it?
Occlusion of brachial artery with BP cuff causing carpal spasm - caused by hypocalcemia (hypoparathyroidism).
SSX of hyperparathyroidism.
Cystic bone lesions, hypercalcemia, hypophosphatemia, increased urinary cAMP
Anatomically, where are beta cells located in the islets?
In the center
HLA association with type I DM
HLA DR3 and DR4. Need to see inflammation of the islets.
How does obesity cause type II DM?
Decreased # of insulin receptors on peripheral tissues.
Histology of type II DM
Amyloid deposition in islets
What is the feared complication of type II DM?
Hyperosmolar non-ketotic coma - high glucose levels cause life threatening diuresis. Ketones are absent because the patient is still releasing some insulin.
What happens with non-enzymatic glycosylation of large/medium sized vessels in a diabetic patient?
Atherosclerosis (CVD, non-traumatic amputations)
What happens with non-enzymatic glycosylation of small vessels in a diabetic patient?
Hyaline arteriolosclerosis (especially in the kidney - preferential involvement of efferent arteriole).
What happens with non-enzymatic glycosylation of hemoglobin in a diabetic patient?
HbA1c
What causes neuropathy in diabetics?
Schwann cells are not insulin dependent. In DM, they take up sugar and aldose reductase converts them to sorbitol, leading to osmotic damage.
What cells are damaged in DM to cause blindness?
Pericytes of retinal blood vessels - aldose reductase converts sugar to sorbitol, pericytes die.
How do cataracts form in DM?
Glucose taken into cell, converted by aldose reductase to sorbitol, causes accumulation of crystallin proteins and cataracts.
Components of MEN 1
Pancreatic endocrine tumor; Parathyroid hyperplasia; Pituitary adenoma
Components of MEN 2A
Parathyroid tumors; Pheochromocytoma; Medullary thyroid cancer
Components of MEN 2B
Oral ganglioneuroma; Medullary thyroid CA, Pheochromocytoma; Marfan habitus
What MEN is associated with a Marfan habitus?
2B
What MEN is associated with oral ganglioneuroma?
2B
What MEN is associated with VIPoma?
1
What MEN is associated with insulinoma?
1
What MEN is associated with gastrinoma?
1
What MEN is associated with pheochromocytoma?
2A, 2B
<p>What MEN is associated with pituitary tumors?</p>
<p>1</p>
what connects the tongue toe the thyroid during development?
thyroglossal duct
normally disappears but may persist as pyramidal lobe of the thyroid
What is the normal remnant of the thyroglossal duct?
Foramen cecum
Where is the most common extopic thyroid tissue site?
tongue
how would a thyroglossal duct cyst present?
An anterior midline neck mass that moves with swallowing
How would a branchial cleft cyst present?
persistent cervical sinus - lateral neck mass
what controls cortisol secretion in a fetus?
ASTH and CRH from fetal pituitary and placenta
What is the most common tumor of the adrenal medulla in adults?
Pheochromocytoma
What is the most common tumor of the adrenal medulla in children?
Neuroblastoma
Where does the left adrenal gland drain?
Left adrenal to the left adrenal vein to the left renal vein to the IVC
Where does the Right adrenal gland drain?
Right adrenal to the right adrenal vein to the IVC
What hormones are secreted from the posterior pituitary?
ADH and oxytocin
What nucleus from the hypothalamus makes ADH?
Supraoptic nucleis
What nucleus from the hypothalamus makes oxytocin?
Paraventricular nucleus
What is the posterior pituitary derived from?
Neuroectoderm
What is the anterior pituitary derived from?
Oral ectoderm (Rathke’s pouch)
Which hormones share a similar alpha unit?
TSH, FSH, LH and hCG
Which subunit of a hormone determines its specificity?
Beta subunit
what hormone is secreted by each of the pancreatic islets and where are they located?
alpha = glucagon = peripheral beta = insulin = central delta = somatostatin = interspersed
Name two things that can increase ADH levels
Nicotine and opiates
Name three things that can decreased ADH levels?
Ethanol, ANP, and decreased serum osmolarity
What is the role of FSH in males and females?
Males - stimulate spermatogenesis
Females - follicular development and stimulates granulosa cells
What is the role of LH in males and females?
Males - stimulate testosterone production via leydig cells
females - stimulates ovulation and forming of the corpus luteum, acts on theca lutein cells to make estrogen and progesterone
What hormones can inhibit FSH?
Inhibin or constant GnRH release
What hormones can inhibit LH?
Progesterone or testosterone or constant GnRH release
Which hormones are developed from POMC?
Pro-opiomelanocortin = ACTH, MSH, and Beta endorphins
What hormone stimulates and inhibits prolactin release?
Stimulated by Thyroid releasing hormone and inhibited by dopamine
How can you differentiate between a person with an insulinoma or exogenous insulin use?
Exogenous insulin use will not result in an increase of C-peptide
an insulinoma will cause an increased in C-peptide
Does insulin cross the placenta?
no
Describe how glucose regulates insulin release?
Glucose enters the beta cells via GLUT-2 channels. The ATP generated by glucose metabolism (glycolysis) closes K+ channels and depolarizes the beta cell membrane.
This leads to the opening of voltage gated Ca2+ channels which leads tot he secretion of insulin
Describe GLUT-1 channels
These are insulin independent channels - found on RBCs and the brain
Describe GLUT-2 channels
Bidirectional channels - found on Beta islet cells, liver, kidney and small intestine
Describe GLUT 4 channels
Insulin dependent channels - found on adipose tissue and skeletal muscle
note that obesity DECREASES the number of these channels
Describe GLUT-3 channels
located on neurons and in the placenta
Describe GLUT-5 channels
Responsible for fructose uptake in the GI tract
Name 3 things that increased insulin?
Hyperglycemia, growth hormone, Beta-2 agonists
Note that GH increases insulin resistance leading indirectly to increased insulin secretion
Name 3 things that decrease insulin?
Hypoglycemia, somatostatin and alpha-2 agonists
what does the brain depend on in times of starvation?
glucose under normal circumstances and ketone bodies in starvation
Name the catabolic functions of glucagon?
Glycogenolysis, gluconeogenesis
Lipolysis and ketone production