Endocrinology Flashcards

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Questions and Answers

Which of the following are features of polypeptide/protein hormones? (Select all that apply)

Hydrophobic

Receptors on cell surfaces (correct)

Circulate unbound (correct)

Large >500 kDa (correct)

What are examples of polypeptide/protein hormones?

LH, FSH, catecholamines, ACTH, TSH, prolactin, GH, GHRH, CRH, GnRH, AVP, PTH, VIP, glucagon, insulin, somatostatin, IGF-I.

Which of the following are features of steroid/thyronine hormones? (Select all that apply)

Small (correct)

High urinary concentration

Low bioavailability

Hydrophilic

What regulates ADH secretion?

Osmoreceptors in the hypothalamus and atrial & carotid baroreceptors. Signup and view all the answers

What hormones stimulate ADH secretion?

Angiotensin II, epinephrine, cortisol, estrogen, progesterone. Signup and view all the answers

What inhibits the secretion of ADH?

Alcohol (EtOH). Signup and view all the answers

What drugs stimulate the secretion of ADH?

Hydrochlorothiazide, chlorpropamide, morphine, propranolol, barbiturates, nicotine, oxytocin, carbamazepine. Signup and view all the answers

What are stimuli for the secretion of ADH?

Hemoconcentration, hypovolemia/hypotension, increasing temperature, nausea/vomiting, hormones, drugs. Signup and view all the answers

What is the threshold for ADH release and thirst stimulation?

Plasma osmolality >285 osm/L. Signup and view all the answers

What should a differential diagnosis for a patient with polyuria include?

Diabetes mellitus, Cushing's syndrome, glucocorticoid therapy, psychogenic polydipsia, nocturnal polyuria, lithium use, diabetes insipidus, hypercalcemia. Signup and view all the answers

What is characterized by excess urine volume >2L/day with low specific gravity?

Diabetes insipidus. Signup and view all the answers

When ADH is not present or inactive, where can water not be conserved?

The distal collecting tubules. Signup and view all the answers

What are causes of central diabetes insipidus?

Hypothalamic or pituitary surgery, trauma, infections, tumors, pituitary infarction, inflammation. Signup and view all the answers

What are causes of nephrogenic diabetes insipidus?

Medications (lithium, demeclocycline), chronic renal disease, pyelonephritis, hypokalemia, chronic hypercalcemia, sickle cell anemia, myeloma. Signup and view all the answers

What should you suspect in patients with persistent urinary incontinence or bedwetting?

Partial diabetes insipidus. Signup and view all the answers

What tests will aid in the diagnosis of diabetes insipidus?

Plasma and urine osmolality, water deprivation test, 24-hour urine tests. Signup and view all the answers

How do you perform the Vasopressin Challenge Test?

Measure urine volume, administer dDAVP, measure urine volume again, assess serum sodium, consider MRI. Signup and view all the answers

If a patient has central diabetes insipidus and you administer the Vasopressin Challenge Test, what will you see?

Decreased thirst, decreased urine output, increased urine osmolality. Signup and view all the answers

If you measure serum vasopressin in a patient with suspected diabetes insipidus and find elevated levels, what does that indicate?

Nephrogenic diabetes insipidus. Signup and view all the answers

What is a complication of nephrogenic diabetes insipidus?

Hypernatremia. Signup and view all the answers

What is the treatment for central diabetes insipidus?

Refer to neurologist & endocrinologist, desmopressin acetate. Signup and view all the answers

How should acute nephrogenic diabetes insipidus be treated?

Treat with indomethacin. Signup and view all the answers

What might a nephrologist do for a patient with nephrogenic diabetes insipidus?

Combine indomethacin with HCTZ, desmopressin, or amiloride. Signup and view all the answers

How do HCTZ and amiloride help in nephrogenic diabetes insipidus?

They produce hyperosmolar urine while decreasing urine output. Signup and view all the answers

What is the treatment for chronic or mild diabetes insipidus?

Maintain adequate water intake. Signup and view all the answers

What are characteristics of SIADH?

Normal vascular volume with hyponatremia, inappropriate ADH secretion. Signup and view all the answers

What are some causes of SIADH?

Tumors secreting ectopic ADH, medications, lesions in the pathway of receptors. Signup and view all the answers

What percentage of lung tumors are associated with SIADH?

80%. Signup and view all the answers

What medications or drugs can induce SIADH?

Antidepressants, antineoplastic agents, MDMA, NSAIDs, narcotics, cytotoxic therapy, hypothyroidism. Signup and view all the answers

What CNS disorders can cause lesions in the pathway of receptors that lead to ADH disorders?

Stroke, subarachnoid hemorrhage, meningitis, encephalitis, trauma, brain tumors. Signup and view all the answers

What may a patient with SIADH present with?

Fatigue, headache, nausea, anorexia, progressing to vomiting and neurogenic impairment. Signup and view all the answers

At what serum sodium level must you urgently treat hyponatremia?

Below normal ranges, typically <130 mEq/L. Signup and view all the answers

Study Notes

Polypeptide/Protein Hormones

Large molecules greater than 500 kDa, hydrophilic, and circulate unbound in the bloodstream.
Short serum half-life (T1/2) of minutes, with receptors located on cell surfaces.
Utilize second messengers to alter activity of intracellular molecules.

Examples of Polypeptide/Protein Hormones

Common hormones include LH, FSH, catecholamines, ACTH, TSH, prolactin, GH, GHRH, CRH, GnRH, AVP, PTH, VIP, glucagon, insulin, somatostatin, and IGF-I.

Steroid and Thyronine Hormones

Small in size with a urinary concentration impact.

Regulatory Mechanisms of ADH Secretion

Osmoreceptors in the hypothalamus detect blood osmolality.
Atrial and carotid baroreceptors monitor circulating blood volume.

Stimuli for ADH Secretion

Stimulated by angiotensin II, epinephrine, cortisol, estrogen, and progesterone.

Inhibition of ADH Secretion

Done by alcohol (EtOH).

Drugs Stimulating ADH Secretion

Includes hydrochlorothiazide (HCTZ), chlorpropamide, morphine, propranolol, barbiturates, nicotine, oxytocin, and carbamazepine.

Factors Triggering ADH Secretion

Hemoconcentration, hypovolemia/hypotension, increasing temperature, nausea, vomiting, hormones, and drugs.

Threshold for ADH Release and Thirst Stimulation

Plasma osmolality greater than 285 osm/L is the threshold; normal range is 275 - 300 osm/L.

Differential Diagnosis for Polyuria

Consider diabetes mellitus (DM), Cushing's syndrome, glucocorticoid therapy, psychogenic polydipsia, nocturnal polyuria (Parkinson's), lithium use, diabetes insipidus (DI), and hypercalcemia.

Symptoms of Diabetes Insipidus

Characterized by excess urine volume (>2L/day) with low specific gravity (decreased osmolality) and intense polydipsia (fluid intake 2-20L/day). May involve hypernatremia, dehydration, hypotension, and vascular collapse.

ADH Action and Water Conservation

Water cannot be conserved in distal collecting tubules when ADH is absent or inactive.

Causes of Central Diabetes Insipidus

Includes hypothalamic or pituitary surgery, trauma to the pituitary stalk, infections (encephalitis, syphilis, TB), tumors, pituitary infarction (e.g., Sheehan's syndrome), and autoimmune hypophysitis.

Causes of Nephrogenic Diabetes Insipidus

Medications (lithium, demeclocycline, methicillin), chronic renal disease, pyelonephritis, hypokalemia, chronic hypercalcemia, sickle cell anemia, and myeloma.

Persistent Urinary Incontinence/Bedwetting

Suspect partial DI, which presents with less intense symptoms.

Diagnostic Tests for Diabetes Insipidus

Plasma and urine osmolality, water deprivation test, 24-hour urine analysis (volume, glucose, creatinine, osmolality), serum analysis (glucose, BUN, calcium, uric acid, sodium, potassium, creatinine, osmolality), and thorough history and physical examination.

Vasopressin Challenge Test Procedure

Measure urine volume for 12 hours before administering dDAVP, then measure again after administration and check serum sodium if hyponatremia is present. MRI may also be conducted.

Central DI Response to Vasopressin Challenge

In central DI, expect decreased thirst, decreased urine output, and increased urine osmolality after administering dDAVP.

Elevated Serum Vasopressin Indicative of Nephrogenic DI

Elevated levels suggest nephrogenic DI rather than central DI.

Hypernatremia as a Complication

Nephrogenic DI can lead to hypernatremia.

Treatment for Central Diabetes Insipidus

Refer to neurologists and endocrinologists; use desmopressin acetate at the lowest effective dose with various administration routes.

Acute Nephrogenic DI Management

Treat with indomethacin (50mg every 8 hours).

Nephrology Management for Nephrogenic DI

Combine indomethacin with HCTZ, desmopressin, or amiloride.

Effects of HCTZ and Amiloride

Both medications help produce hyperosmolar urine while reducing urine output.

Management of Chronic/Mild Diabetes Insipidus

Emphasize maintaining adequate water intake.

Characteristics of SIADH

Presents with normal vascular volume but hyponatremia; involves inappropriate ADH secretion without osmotic stimulus, decreased plasma osmolality, and inappropriate urine concentration.

Causes of SIADH

Include tumors that secrete ectopic ADH and drug-induced cases.

Lung Tumors and SIADH Correlation

Approximately 80% of lung tumors are associated with SIADH.

Medications Inducing SIADH

Antidepressants, antineoplastic agents, MDMA, NSAIDs, narcotics, cytotoxic therapy, and hypothyroidism/hypoadrenalism.

CNS and Pulmonary Disorders Causing SIADH

Associated disorders include stroke, subarachnoid hemorrhage, meningitis, encephalitis, trauma, brain tumors, and pulmonary diseases like TB and bacterial pneumonia.

Symptoms of SIADH

Presents with fatigue, headache, nausea, and anorexia progressing to vomiting and neurogenic impairment due to hyponatremia.

Urgent Treatment Threshold for Hyponatremia

Urgent treatment required when serum sodium falls below 135 mEq/L.

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Description

Test your knowledge of polypeptide and protein hormones with these flashcards. This quiz covers definitions, features, and examples of important hormones in endocrinology. Perfect for students or anyone interested in the field of medicine.