Endocrinology Flashcards
From what is the anterior pituitary derived?
Rathke’s Pouch
What is the function of the hypothalamic-pituitary portal plexus in addition to providing blood to the ant. pituitary?
Transmission of hypothalamic peptides w/o systemic dilution
What is the function of dopamine release in regulation of prolactin?
Inhibits prolactin
What is the function of Somatostatin Releasing Inhibitory Factor (SRIF) in regulation of Growth Hormone?
Inhibits GH
What is the function of Gonadotropin Releasing Hormone?
Release of FSH and LH
What is the function of Thyrotropin Releasing Hormone?
Release of Thyroid Stimulating Hormone
Release of Prolactin
What is the function of Growth Hormone Releasing Factor (GHRF)?
Release of GH
What is the function of Somatostatin Releasing Inhibitory Factor (SRIF)?
Inhibits GH release
What is the function of Corticotropin Releasing Hormone?
Release ACTH
What hormones are in the group Somatomammotropins?
GH
Prolactin
(act on tissue)
What hormones are in the group Corticotropins?
ACTH
What hormones are in the group Glycoproteins?
TSH
FSH
LH
What is the function of GH?
- Promote linear growth
- Increases free fatty acids
- Increases glucose concentratio
- Stimulates Immune system
What is the function of Prolactin? How can it effect men?
- Function
- Lactation
- enlargement of mammary glands
- Disrupts menses
- Lactation
- Men
- Hypogonadism
What is the function of ACTH? What stimulates its release?
- Function
- Stimulates cortisol production
- Stimulated by
- Stress
How is TSH regulated?
- Stimulated by
- TRH
- Inhibited by
- Somatostatin
- DA
- Excess glucocorticoids
Sensitivity of thyrotrophs improved by estrogen
What is the function of LH and FSH in males?
- LH
- Stimulates Leydig = testosterone production
- FSH
- Androgen binding
- Both
- Sperm maturation
In males, what inhibits FSH?
Inhibin, made by Sertoli cells
What is the function of LH and FSH in females?
- LH
- Estrogen production
- Progesterone production
- Ovulation
- FSH
- Maturation of follicle
- Both
- Estrogen from follicle
What regulates the posterior pituitary?
Anterior Hypothalamus
What is the most important function of ADH?
Water balance
What is the function of Oxytocin?
- Lactation
- Contractions (uterus)
What are the long and short feedback loops of the hypothalamic-pituitary axis?
- Long:
- hormones from target tissue gives feedback (inhibition) to the hypothalamus/pituitary
- Short:
- Pituitary hormones inhibit hypothalamus
Cortrosyntropin test
- Use
- Significance
- Use
- Determine the cause of low hormone
- Hypothalamus, pituitary, adrenal
- Significance
- Cause is Hypothalamic
- ACTH and Cortisol / Aldosterone production is normal with CRH
- Cause is Pituitary
- Low ACTH production
- Cause is Adrenals
- Low cortisol and aldosterone
- Cause is Hypothalamic
What is the most common presenting symptom of Craniopharyngioma in children? Adults?
- Children
- GH deficiency
- Growth retardation
- Adult
- Visual problems
- compression of optic chiasm
- Later have symptoms resulting in Mass Effect
- Visual problems
What is the most common visual finding in pituitary tumor?
Bitemporal hemianopsia
What signs result from encroachment of pituitary tumors into the cavernous sinus?
- Contents
- Internal carotid
- CN III, IV, VI, V1, V2
- (CN III has parasympathetic fibers)
- Signs
- Eye movement problems
- Pupillary / parasympathetic signs
- Loss of sensation of face
What are the symptoms of spontaneous infarction of a pituitary tumor?
Associated with raised intracranial pressure
- Headache
- Nausea/vomiting
- Ocular palsy
- Visual field defect
- May have pituitary failure with adrenal insufficiency
Sheehan Syndrome
- Cause
- Pop with higher risk
- Symptoms
- Cause
- Pregnancy causes enlarged pituitary w/o change in blood flow
- Postpartum hemorrhage or shock causes decreased flow to pituitary
- necrosis
- Pop
- Diabetics
- Symptoms
- inability to breast-feed
- Lack of menstrual bleeding
- Late: loss of pubic and axillary hair
What are the most common hypersecreted hormone in Pituitary Adenoma?
- Prolactin
- GH
Hyperprolactinemia
- Symptoms
- Treatment
- Symptoms
- Galactorrhea
- Amenorrhea
- Impotence (men)
- Treatment
- Dopamine agonists
- Trans-shenoidal approach
- removal
- Radiation of pituitary
Adult Onset Growth Hormone Deficiency
- Cause
- Symptoms
- Cause
- pituitary adenomas
- Parasellar tumors (push on stalk)
- Symptoms
- Loss of lean muscle
- Reduced bone mass
- Altered glucose metabolism
- Raised LDL
What results from Growth Hormone Secreting Adenomas?
- Children
- Gigantism
- Excess IGF-1
- Delayed closure of epiphysis
- Gigantism
- Adults
- Acromegaly
- GH regulation by glucose lost
- Excess IGF-1
- Overgrowth of soft tissues and organs
- Acromegaly
What is Pseudoacromegaly?
Acromegaloid features w/o increased GH and IGF-1
Associated with insulin resistance
Diagnosis and treatment of Acromegaly
- Diagnosis
- IGF-1 levels
- Glucose suppression test
- Serial Photographs
- Treatment
- Somatostatin analog
- Transsphenoidal surgery
- Radiotherapy
What are the symptoms of Diabetes Insipidus? What is the physiologic mechanism leading to these symptoms?
- Symptoms
- polyuria
- polydipsia
- Physio
- Kidneys cannot concentrate urine
- Lack of ADH function
What is the difference between Central and Nephrogenic ADH (insensitivity)?
- Central
- Partial or total loss of ADH secretion
- Nephrogenic
- Renal resistance to ADH
What causes Gestational DI?
Degradation of vasopressin by placental vasopressinase
What is the initial testing for DI?
Water deprivation test
Failure to concentrate urine suggests DI
How can central vs nephrogenic DI be determined clinically?
- Injection of arginine vasopressin
- If urine concentrates = Central
- If it doesn’t = Nephrogenic
What is primary polydipsia?
Defect in osmoregulation of thirst
How can Primary Polydipsia be distinguished from DI?
- DI
- Urine osm < plasma osm
- 50% improvement with vasopressin
- PP
- Urine osm > plasma osm
- Little response to vasopressin
How are central and nephrogenic DI treated?
- Central
- Vasopressin analog
- Nephrogenic
- Treat underlying disease
- hypokalemia or hypercalcemia
- Treat underlying disease
What are the clinical signs of SIADH?
- Hyponatremia
- Elevated urine osmolality
- Decreased serum osmolality
- Patient is EUVOLEMIC
Excess ADH causes resorption of lots of water, resulting in Dilutional Hyponatremia
What is the most common malignant cause of SIADH?
Small Cell Lung Cancer
What is the treatment of SIADH? What severe complication can result?
- Treatment
- Long-term water restriction
- Correct hyponatremia
- Complication of correcting hyponatremia too rapidly
- Cerebral edema
- Central pontine myelinolysis
- decreased consciousness
- Quadriparesis
- Dysphagia
- Mutism
What features differentiate DI and SIADH?
What is the metabolically active form of thyroid hormone? Where is it produced?
T3
Produced in periphery from deiodination of T4
What are the functions of thyroid hormone?
- Stimulates thermogenesis
- Metabolism
- Potentiates action of catecholamines
- Stimulate growth and development
- esp brain and skeleton
Free T4 (FT4) Test
- What does it reflect?
- Normal?
- Reflects
- metabolic status
- Unaffected by serum proteins or non-thyroid illness
- Normal
- 0.8-1.6
What does the Free T3 (FT3) Test reflect?
Not routinely used
For what is the T3 Test used?
Hyperthyroidism
Determines severity and response to treatment
What does T3 Uptake measure?
Indirectly measures TBG
Test rarely used
For what is Radioactive Iodine Uptake used?
Differentiates between
- Subacute thyroiditis
- Always suppressed in acute phase
- Hyperthyroidism / Graves
- Elevated
Thyroid Peroxidase Abs (TPO) and Anti-Thyroglobulin Abs are most common in what disease? In what others can it be found?
- Most common
- Hashimoto’s thyroiditis
- Others
- Graves
- Subacute thyroiditis
When are TPO and Anti-thyroglobulin Abs used?
Patient with modest elevation of TSH
What is the diagnosis if a patient has normal TSH and Free T4 levels but test positive for TPO and Anti-Thyrglobulin Ab?
Increased risk of developing hypothyroidismin the future
Thyroid stimulating Abs are produced in what disease? Where do they bind, and what are the resulting symptoms?
Graves Disease
- Binds
- TSH receptor in thyroid = Increased TH
- Eyes = exophthalmos
- Skin surface = myxedema
Patient presents with anterior neck pain, myalgia, low fever, and a sore throat. PE shows a hardness of the thyroid. Labs results show elevation of ESR, Elevation of T3 and T4, decreased TSH, and suppressed RAIU. What is the diagnosis? What is the clinical course of disease?
Subacute Thyroiditis
Initial hyperthyroid w/ decreased TSH, but transient
What is the most common Primary Hypothyroidism in the US?
Hashimoto’s
What is the most common cause of Acquired primary hypothyroid?
Hashimoto Thyroiditis
What antibodies are present in Hashimoto Thyroiditis?
Anti-thyroglobulin
WHat is the best screening test for Hypothyroidism?
TSH
What is the most common cause of Congenital Hypothyroidism?
Thyroid dysgenesis
May have agenesis, ectopic, or hypoplastic thyroid
When is the best time to chech TSH in a newborn? Why?
After 24 hours
B/c there is a surge of TSH w/i the first 24 hours of delivery
What complication of hypothyroidism in an infant can occur if treatment is delayed?
Decreased cognitive abilities, Decreased growth
(TH associated with development of brain & skeleton)
What is Euthyroid Sick Syndrome? What is the treatment?
- Syndrome
- Severe Illness causes decreased T3
- Impaired conversion in the periphery
- Treatment
- None
- Watch levels
What is the most common cause of Hyperthyroidism?
Graves Disease
Lab results for a patient show the presence of TPO Abs, Low TSH, Elevated Free T4, Elevated T3, Positive TSI, and Increased RAIU. What is the diagnosis?
Graves disease
Positive TSI = Graves
Increased RAIU = differentiates from subacute thyroiditis or hyperfunctioning nodule
What is the most important lab test to determine severity of Graves Disease?
Thyroid Stimulating Immunoglobulin (TSI)
Correlates with severity of disease
What HLA type is associated with an increased risk of Graves Disease?
HLA-DR3
What is the goal of radioablation?
Induce permanent Hypothyroidism