Endocrinology Flashcards
srif(somatostatin from hypothalamus)
Negative to prolactin and TSH
GH on liver
Chondrocytes-linear and organ growth
IGF-1 negative on hypothalamus
Prolactin
Increase breast
TSH on thyroid
T4/T3
Pituitary adenoma
Benign monoclonal tumors that arise from one of five pituitary cell types
Nonfunctional pituitary adenoma
1/3 no clinical symptoms
Most common functional pituitary tumor
PRL
Genetics pituitary adenoma
MEN1, carney, mutant Arya hydrocarbon receptor inhibitor protein (AIP).
Mass effect symptoms
HA, visual loss through compression of the optic chiasm superiorly (bitemporal hemianopia)
Pituitary stalk compression
HyperPRL
Pituitary apoplexy
Hemorrhage into a preexisting adenoma or post partum as sheehans syndrome
HA< bitemporal changes, ophthalmoplegia, cardiovascular collapse, hypotension,
Hypotension, hypoglycemia, can hemorrhage, death
Treat pituitary apoplexy
Glucocorticoids, surgical decompression though when visual or neurologic symptoms are present
Diagnose pituitary adenomas
Sagittarius and coronal T1 weighted MRI before and after gadolinium
Visual field assessment if close to chiasm
How see pituitary apoplexy
CT or mRI of the pituitary may reveal signs of stellar hemorrhage with deviation of the pituitary stalk and compression of pituitary tissue
Treat pituitary tumor with surgery
Surgery if mass lesion that impinge on structures or correct hypersecretion BUT DOENST WORK IN HYPER PRL
Goal of surgery for pituitary
Resection without damage to normal pituitary tissue to decrease chance of hypopituitarism,
Post op risk of pituitary adenoma
DI, hypopit, CSF rhinorrhea, vision loss, oculomotor palsy
Radiation
Adjunct to surgery , but efficacy delayed and 50% get hormonal defiencies within 10 years
PRL tumor treat
Drugs
Prolactin function
Induce and maintain lactation and decrease reproductive function and drive (via suppression of gonadotropin releasing hormone, gonadotroph is, and gaonadal , steroidogenesis)
Physiologic elevation prolactin
Pregnancy and lactation
Most common non physiologic cause of prolactin >100 microg/L
Pituitary adenoma
Meds (risperidone, chlorpromazine, perphenazine, haloperidol, metoclopramide, opiates, H2 antagonists, amitriptyline, SSRI, verampamil, estrogens), pituitary stalk damage, renal failure
Nipple stimulation
Women hyperprolactinemia
Amenorrhea, glactorrhea, infertility
Men hyperprolactinemia
Hypogonadism, mass effects and rarely galactorrhea
Diagnose hyperprolactinemia
Fasting, morning PRL levels should be measured;
No neoplastic causes should be excluded-pregnancy test, hypothyroidism, medications
Treat hyperprolactinemia
Stop drugs that may be causing it
Pituitary MRI
Surgery for sellar or hypothalamic mass lesions
Dopamine agonist -shrinkage and reduction of PRL levels and adenoma shrinking
9FOR MICROPROLACTINOMAS)
Estrogen replacement
Cabergoline and bromocriptine
GH hypersecretion
Somatotroph adenomas
MEN1, carney, mcCune albright, familial AIP mutations
Rare for extrapituitary causes
Clincial features acromegaly
40-45
Delayed diagnosis of a decade
Facial features, widened teeth spacing, deepening of the voice, snoring, increased shoe or glove size, ring tightening, hyperhidrosis, oily skin, arthropathy, carpal tunnel syndrome.
Cardiomyopathy, left ventricular hypertrophy, diastolic dysfunction, sleep apnea, glucose intolerance, DM, colon polyps, colonic malignancy
Gigantism
Before epiphysis closes
Diagnose hyperGH
IGF-1 levels are useful screening , elevation suggests acromegaly
Need more than 1 time
Confirmed with oral glucose load test,
RI usually macroadenomas-delayed onset
Treat acromegaly
Transsphenoidal surgery*
Somatostatin analogues (ocreotide,)
Dopamine agonists in adjunct
GH receptor antagonist (pegvisomant)
Pituitary irradiation)
Gonadotropin producing adenoma
FSH intact and LHb and FSHb subunits, which are uncombined a subunits
Treat gonadotropin producing adenoma
Surgery for mass effects or hypopituitarism
If small follow with regular MR and visual field test
Diagnose Gonadotropin adenomas
Immunohistochemical analyisis of resected tumor tissue
TSH adenoma
Rare, large and locally invasive
Hyperthyroidism and/or sella mass effect
Diagnosis TSH adenomas
Elevated T4 levels in the setting of inappropriately normal or high TSH secretion and MRI evidence of a pituitary adenoma.
Surgery is indicated and is usually followed by somatostatin analogue therapy to treat residual tumor
Somatostatin analogue therapy
Thyroid ablation or antithyroid drugs can be used to reduce thyroid hormone levels
Most common cause of hypopituitarism
Neoplastic (macroadenomatous destruction,or following hypophysectomy or radiaiton therapy)
Sequential pattern that pituitary hormone failure follows
GH>FSH>LH>TSH>ACTH
Hypopituitarism following cranial irradiation develops
Over 5-15 years
Hypo GH
growth disorders in children; increased intraabdominal fat, reduced lean body mass, hyperlipidemia, reduced bone mineral density, decreased stamina, and social isolation in adults
Hyp FSH LH
Menstrual disorders and infertility in women; hypogonadism in men
ACTH
Features of hypocortisolism without mineralocorticoid defiency
hypo TSH
Growth retardation in children; features of hypothyroidism in children and adults
Hypo PRL
Failure to lactate postpartum
Diagnose hypopituitarism
Low levels of hormones in setting of low target hormone levels
8 am cortisol level, TSH< free T4, IGF-I, testosterone in men, associated menstrual cycles in women, and PRL level
Provocative tests for definitive diagnosis of GH and ACTH defiency**
Insulin tolerance test for GH
Insulin tolerance, metyrapone test, or CRH stimulation test for ACTH
Treat hypopituitarism
Hormonal replacement
GH therapy
Fluid retention, joint pain, carpal tunnel
Glucorticoid replacement
Always precede I-thyroxine therapy to avoid precipitation of adrenal crisis.
What else is posterior pituitary called
Neurohypophysis
ADH
Acts on renal tubules to induce water retention, leading to concentration of the urine.
Oxytocin
Stimulates postpartum milk letdown in response to sucking
Diabetes insipidus
Insufficient ADP production prom hypothalamus or impaired action in kidney
Central DI
Insufficient release
-head trauma,neoplastic, inflammatory, congenital, genetic, MOST IDIOPATHIC
Gestational DI
Increased metabolism of plasma ADH by an aminopeptidase produced by the placenta leads to a relative defiency of AVP during pregnancy
Primary polydipsia
Results in secondary insuffiency of ADH due to physiologic inhibiton of ADH secretion by excessive fluid intake
Nephrogenic DI
ADH resistance at the level of the kidney; it can be genetic or acquired from drug exposure (lithium, demeclocyline, amphotericin B), metabolic conditions (hypercalcemia, hypokalemia) or renal damage
Clincial features DI
Polyuria, excessive thirst, polydipsia with 24 hour urineoutput of >50 ml/kg per day and urine osmolarity that is less than that of serum (<300, specific gravity<1.01)
Clinical or laboratory signs of dehydration
Hypernatremia, occur only of the pt simultaneously has a thirst defect (not uncommon in patients with CNS disease) or does not have access to water.
Diagnose DI
Must be differentiated from other causes of polyuria
Fluid deprivationt est.
-morning
Measure body weight, plasma osmolarity, serum sodium, and urine volume and osmolality every hour)
-stop tes with body weight decreases 5% or plasma osmolality/sodium exceeds the upper limit of normal.
If the urine osmolality is <300 mosmol/kg with serum hyperosmolality, desmopressin (0.03 μg/kg SC) should be administered with repeat measurement of urine osmolality 1–2 h later. An increase of >50% indicates severe pituitary DI, whereas a smaller or absent response suggests nephrogenic DI. Measurement of AVP levels before and after fluid deprivation may be helfpul to distinguish central and nephrogenic DI. Occasionally, hypertonic saline infusion may be required if fluid deprivation does not achieve the requisite level of hypertonic dehydration, but this should be administered with caution
Treat DI
Desmopressin subcutaneousl, nasal spray, or oral
Thiazide diuretic and/or amiloride with low na diet or prostagladin synthesis
SIADH
Hyponatremia, reflecting water retention
Cause of SIADH
Neoplasma, lung infections, CNS disorders, drugs
Clincial features SIADH
If hyponatremia develops gradually, it may be asymptomatic until it reaches a severe stage. However, if it develops acutely, symptoms of water intoxication may include mild headache, confusion, anorexia, nausea, vomiting, coma, and convulsions. Laboratory findings include low BUN, creatinine, uric acid, and albumin; serum Na <130 meq/L and plasma osmolality <270 mosmol/kg; urine is not maximally diluted and frequently hypertonic to plasma, and urinary Na+ is usually >20 mmol
Treat SIADH
TREATMENT: SIADH
Fluid intake should be restricted to 500 mL less than urinary output. In pts with severe symptoms or signs, hypertonic (3%) saline can be infused at ≤0.05 mL/kg body weight IV per minute, with hourly sodium levels measured until Na increases by 12 meq/L or to 130 meq/L, whichever occurs first. However, if the hyponatremia has been present for >24–48 h and is corrected too rapidly, saline infusion has the potential to produce central pontine myelinolysis, a serious, potentially fatal neurologic complication caused by osmotic fluid shifts. Vasopressin antagonists (conivaptan, tolvaptan) are now available, but experience with these agents in SIADH treatment is limited. Oral vaptan (tolvaptan), a selective V2 antagonist increases urinary water excretion by blocking the antidiuretic effect of AVP. It should be initiated in the hospital (typically 15 mg PO qd) to evaluate the clinical response and avoid excessive diuresis. Other options include demeclocycline, 150–300 mg PO tid or qid, or fludrocortisone, 0.05–0.2 mg PO bid. The effect of the demeclocycline manifests in 7–14 days and is due to induction of a reversible form of nephrogenic DI. The effect of fludrocortisone also requires 1–2 weeks and is partly due to increased retention of sodium and possibly inhibition of thirst. It also increases urinary potassium excretion, which may require replacement through dietary adjustments or supplements and may induce hypertension
Thyroid
Thyroidal production of the hormones thyroxine (T4) and triiodothyronine (T3) is controlled via a classic endocrine feedback loop (see Fig. 168-1). Some T3 is secreted by the thyroid, but most is produced by deiodination of T4 in peripheral tissues. Both T4 and T3 are bound to carrier proteins (thyroid-binding globulin [TBG], transthyretin [binds T4], and albumin) in the circulation. Increased levels of total T4 and T3 with normal free levels are seen in states of increased carrier proteins (pregnancy, estrogens, cirrhosis, hepatitis, and inherited disorders). Conversely, decreased total T4 and T3 levels with normal free levels are seen in severe systemic illness, chronic liver disease, and nephrosis
Deficient thyroid hormone
Thyroid failure
Pituitary or hypothalamic disease
Congenital
Lab hypothyroidism
TSH high, low T4
Iodine suffiency and hypothyroidism
autoimmune disease and iatrogenic causes are the most common etiologies of hypothyroidism
Age hypothyroidism
The peak age of occurrence is around 60 years, and prevalence increases with age
Symptoms hypothyroidism
Lethargy, dry hair an skin, cold intolerance, hair loss, diffficulty concentrating, poor memory, constipation, mild weight gain with poor appetite, dyspnea, hoarse voice, muscle cramping, and menorrhagia
Bradycardia, mild diastolic HTN, prolongation of relaxation phase of DTR, cool peripheral extremities
GOITER
Carpal tunnel, cardiomegaly,
Patient with hypothyroidism
Dull expressionless face, sparse hair, periorbital puffiness, large tongue pale, doughy cool skin
Hypothermic stupendous state from hypothyroidism
Myxedema coma
Factors that predispose to myxedema coma
Cold exposure, trauma, infection, and administration of narcotics
Diagnosis hypothyroidism
Decreased serum free T4 is common to all varieties of hypothyroidism. An elevated serum TSH is a sensitive marker of primary hypothyroidism but is not found in secondary hypothyroidism. A summary of the investigations used to determine the existence and cause of hypothyroidism is provided in Fig. 170-1. Thyroid peroxidase (TPO) antibodies are increased in >90% of pts with autoimmune-mediated hypothyroidism. Elevated cholesterol, increased creatine phosphokinase, and anemia may be present; bradycardia, low-amplitude QRS complexes, and flattened or inverted T waves may be present on ECG