Originally, selenium deficiency as a result of malnutrition was thought to reduce D1 catalytic activity, but this theory has not been supported as a cause of NTIS. NTIS as a result of fasting may be regarded as a healthy and adaptive mechanism that reduces energy expenditure. Fasting in healthy, euthyroid people causes reduced T3 and elevated rT3, although TSH is usually unchanged. Even moderate weight loss can lower T3.This may be primarily via reduced levels of leptin (the satisfaction hormone). Low leptin levels can downregulate hypothalamic TRH neurons and cause a reduction in TSH. Ιn fasting animals, administering leptin reverses NTIS symptoms and restores thyroid hormone concentrations. In obesity, increased leptin increases TSH and T3, and lowers rT3, possibly as an attempt to increase energy expenditure and return to weight set point.Other signals associated with hunger also affect the HPT axis. Insulin and bile acids, which are elevated after a meal, lead to increased D2 activity, therefore increasing T3 and reducing rT3. Low leptin increases NPY and AGRP (associated with appetite), which inhibit TRH gene expression; this effect is enhanced by ghrelin (the hunger hormone). a-MSH stimulates TRH gene expression in the PVN. This is enhanced by leptin, and inhibited by low leptin. a-MSH is also antagonized by AGRP. Alternative phenotype (type 2 thyroid allostasis)
An anti-NTIS phenotype is observed in some circumstances, wherein TSH, T3, and T4 are generally elevated rather than suppressed.
Differential diagnosis
A renal colic must be differentiated from the following conditions:
biliary colic and cholecystitis
aortic and iliac aneurysms (in older patients with left-side pain, hypertension or atherosclerosis)
interstitial: appendicitis, diverticulitis or peritonitis (in this case patients prefer to lie still rather than being restless)
gynaecological: endometriosis, ovarian torsion and ectopic pregnancy
testicular torsion

Treatment
Most small stones are passed spontaneously and only pain management is required. Above 5 mm (0.20 in) the rate of spontaneous stone passage decreases. NSAIDs (non-steroidal anti-inflammatory drugs), such as diclofenac or ibuprofen, and antispasmodics like butylscopolamine are used. Although morphine may be administered to assist with emergency pain management, it is often not recommended as morphine is addictive and raises ureteral pressure, worsening the condition. Vomiting is also considered an important adverse effect of opioids, mainly with pethidine. Oral narcotic medications are also often used.There is typically no antalgic position for the patient (lying down on the non-aching side and applying a hot bottle or towel to the area affected may help). Larger stones may require surgical intervention for their removal, such as shockwave lithotripsy, laser lithotripsy, ureteroscopy or percutaneous nephrolithotomy. Patients can also be treated with alpha blockers in cases where the stone is located in the ureter. References


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