Module 5: Endocrine: DI, SIADH, Graves and Hyperparathyroidism, Thyroid Adenoma Flashcards
First lets start off with Diabetes Insipidus, what is the etiology?
Deficiency or resistance to the action of ADH
There are two different types of Diabetes Insipidus, the first is central DI, what are some features?
Central DI: absolute deficiency of ADH
—genetic, idiopathic or hypothalamic/pituitary stalk disease
The second type of DI is nephrogenic DI, what are some features?
Nephrogenic DI: resistance to ADH action
- -genetic, metabolic (hypokalemia, hypercalcemia) or lithium
- -hypercalcemia causes aquaporin in CD to be insensitive to ADH – decreased urine osmolality — polydipsia and polyuria
What is the function of ADH?
Response to decreased blood volume and increased plasma osmolality (water is absorbed by osmosis into the blood in response to hypovolemia)
- -increased permeability in DCT and CT — water retention and decreased urine volume
- -small volume of urine that is concentrated because all your H20 is being absorbed in the DCT and CT into the blood stream due to dehydration or any state of hypovolemia
What investigations are done for DI?
Water deprivation test:
Central DI: less than 300mosmol/kg and after vasopressin greater than 600mosmol/kg (now water is being reabsorbed so urine can finally concentrate, instead of being super dilute )
Nephrogenic DI: less than 300mosmol/kg and after vasopressin less than 300mosmol/kg (defect is in the kidneys so no matter how much ADH you inject, the urine concentration is not going to change)
Along the same lines as SIADH, what is SIADH?
ADH secretion which continues despite lack of physiological stimuli —- water retention and hyponatremia
–hyponatremia is due to the dilation of sodium by H20 flooding the bloodstream
What is the etiology for SIADH?
Post op
Intra-cranial disease: encephalitis, meningitis, head injury
Neoplasms: small cell carcinoma of the lung
Pulmonary disease: pneumonia and TB
Drugs/Medication
What are the lab values for SIADH?
High urine osmolality (urine is super concentrated because all the water is being absorbed into the blood stream)
Low plasma osmolality (plasma is super dilute because H20 is constantly flooding the bloodstream due to ADH action and the insertion of aquaporins)
Moving onto Hyperthyroidism, what is the most common cause?
Grave’s Disease
- -more common in females b/c its an autoimmune condition — type II HSR
- -HLA association
- -Type I DM and Addison’s alot of the times coincide because of the Type II HSR
What is the etiology for Graves disease?
T cells induce B cells to produce IgG antibodies against the TSH receptor (stimulating Abs)
What is the pathogenesis for Grave’s Disease?
Thyroid Stimulating Ig (TSI): IgG that binds to TSH receptor and mimics action of TSH —- Increased T3/T4
- -T4 is peripherally converted to T3 (Active form)
- -TSI does not respond to negative feedback
What is seen on gross and histology for grave’s disease?
Gross: Very vascular beefy red thyroid and diffusely enlarged (bruit heard on exam because of increased turbulence when you listen)
Histology: Lumen in lined by columnar epithelium (instead of normal cuboidal due to hyperstimulation) and the colloid within the follicular lumen is pale, with scalloped margins (Due to active resorption of the collid)
Hyperactivity of thyroid follicle —- papillary projections into lumen (without fibrovascular core/psamomma bodies)
What investigations are done for Graves Disease?
Radioactive iodine uptake= HOT NODULE (secretes thyroid hormone)
Most accurate test: measure TSI (very high)
–T3 and T4 will be very high
–TRH and TSH will be very low
What is the treatment for Grave’s Disease?
Radioactive iodine ablation — hypothyroidism (give thyroxine treatments b/c hypothyroidism is easy to treat)
In Grave’s Disease there is a triad of symptoms, each card will go through a point in the triad
- Thyrotoxicosis (hyperthyroidism — diffuse goiter — hear bruit) pic 3b
- -thyrotoxicosis is toxicity caused by excess thyroid hormones which may be due to hyperactive thyroid gland or exogenous thyroid hormones
- -weight loss despite increased appetite, fine tremor, diarrhea, sweating and palpitations