Syndrome of inappropriate ADH SIADH

In hypoosmotic hyponatremia with a normal volume status, the most common etiologies are the syndrome of inappropriate ADH (SIADH), primary polydipsia, hypothyroidism, and adrenal insufficiency (see Figure 46-2). SIADH is usually a result of ectopic or otherwise inappropriate ADH production arising from a variety of conditions (see Chapters 45 and 50) and results in excessive H2O retention. SIADH is often diagnosed when a urine osmolality that is greater than plasma osmolality (usually by more than >i00 mOsmol/kg) is observed in the setting of hyponatremia, but only when renal, adrenal, and thyroid functions are normal. Hypothyroidism impairs free H2O excretion, whereas in adrenal insufficiency, Na" is lost in preference to IC reabsorption. Finally, euvolemic hyponatremia can be... 

Severe gastroenteritis (many poisons) Syndrome of inappropriate ADH (SIADH) ... 

Syndrome of Inappropriate ADH (SIADH), and Diabetes (Diabetic Ketoacidosis [DKA] and Hyperosmolar... 

The posterior lobe of the pituitary gland normally releases ADH in response to elevated serum osmolality to direct the kidneys to conserve water and restore fluid concentration balance. A condition referred to as the syndrome of inappropriate ADH (SIADH), in which there is an abnormal production or continued secretion of ADH, will result in excessive retention of water regardless of serum osmolality levels. The characteristic symptoms of SIADH are... 

Syndrome of inappropriate ADH secretion (SIADH) PO Initially, 900-1200 mg/day in 3-4 divided doses, then decrease dose to 600-900 mg/day in divided doses. 

Three cases of fluvoxamine-induced polydipsia, attributed to the syndrome of inappropriate ADH secretion (SIADH), have been reported (SEDA-18, 20). 

ADH antagonists oppose the actions of ADH and other naturally occurring peptides that act on the same Vj receptor. Such peptides are produced by certain tumors (eg, small cell carcinoma of the lung) and can cause significant water retention and dangerous hyponatremia. This syndrome of inappropriate ADH secretion (SIADH) can be treated with demeclocycline. Lithium also works but has greater toxicity. 

Syndrome of inappropriate ADH secretion (SIADH). In patients with SIADH, ADH is secreted independently of volume or osmolality. Causes include malignancies, pulmonary disease, severe head injury, and some dmgs (see Table 1-26). The serum osmolality is low, but the urine osmolality is inappropriately increased (>300 mOsm/L). The serum blood urea nitrogen (BUN) is usually low (<10 mg/dL). 

The syndrome of inappropriate antidiuretic hormone (SIADH) secretion is a condition in which secretion of ADH continues despite serum hypo-osmolarity. This results in fluid retention and hyponatremia that can lead to brain oedema, mental confusion and coma. The causes are hypothalamic-pituitary tumours or an ectopic vasopressin-secreting tumour. 

Furosemide rarely causes the syndrome of inappropriate antidiuretic hormone secretion (SIADH) (although it has been found useful in treating some patients with SIADH who cannot tolerate water restriction (428)). In furosemide-induced cases (SEDA-7, 246), serum ADH concentrations were raised, total body sodium was normal, total body potassium greatly reduced, and intracellular water raised at the expense of extracellular fluid volume. However, such cases are rare, and no new cases have been published since this complication was reported in SEDA-7. 

Hyponatremia is caused by an excess of total body water relative to total body sodium and can result from a number of underlying conditions, including the syndrome of inappropriate antidiuretic hormone secretion (SIADH), cirrhosis, and congestive heart failure (CHF). In each of these conditions, inappropriate production of arginine vasopressin (AVP) [also known as vasopressin or antidiuretic hormone (ADH)], a neurohormone that regulates renal electrolyte-free water reabsorption, contributes to enhanced renal water retention, leading to decreased serum sodium concentrations.7 Hyponatremia can be characterized as hypervolemic, euvolemic, or hypovolemic... 

An unexpected use for a tetracycline is in the treatment of chronic hyponatraemia due to the syndrome of inappropriate antidiuretic hormone secretion (SIADH) when water restriction has failed. Demeclocycline produces a state of unresponsiveness to ADH, probably by inhibiting the formation and action of cyclic AMP in the renal tubule. It is effective and convenient to use in SIADH because this action is both dose-dependent and reversible. 

SIADH syndrome of inappropriate secretion of ADH TSH thyroid-stimulating hormone... 

ADH, Antidiuretic hormone SIADH, syndrome of inappropriate antidiuretic hormone,... 

The tetracyclines block the attachment of aminoacyl tRNA to the acceptor site on the bacterial ribosome. They are broad-spectrum drugs with good activity against chlamydial and mycoplasmal species, as well as against other indicated bacteria. Doxycycline is of particular use in the treatment of prostatitis, minocycline is useful for treating meningococcal carrier states, and demeclocycline is useful for treating the syndrome of inappropriate secretion of ADH (SIADH). Their biodisposition and side effects are discussed. 

Relatedly, malfunction of one of the sodium-water control mechanisms, such as a kidney that normally excretes excess water, can result in fluid retention and dilutional hyponatremia. The pituitary gland and hypothalamus function to release ADH (which controls water reabsorption), and the cortex of the adrenal gland seaetes aldosterone (which controls sodium reabsorption). An alteration in the function of either of these hormone systems will alter the body s regulation of sodium or water and can result in hyponatremia. 2 For example, in the syndrome of inappropriate antidiuretic hormone (SIADH), excessive ADH is produced (usually by a tumor or some pulmonary diseases such as tuberculosis or bacterial pneumonia), and the kidneys reabsorb excessive fluids, resulting in dilutional hyponatremia. Conditions causing decreased aldosterone secretion include... 

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