Vanillylmandelic acid (VMA) and homovanillic acid (HVA) are end products of noradrenaline and dopamine metabolism. VMA and HVA may be determined in either 24-h urine collections or within single spot urine samples. The measurement of 5-hydroxyindoleacetic acid (5-HIAA), the main product of serotonin metabolism is in urine collected over 24h.

Iohexol is an effective non-ionic, water-soluble contrast agent which is used in myelography, arthrography, nephroangiography, arteriography, and other radiographic procedures. Its low systemic toxicity is the combined result of low chemotoxicity and low osmolality.

Endogenous melatonin is a naturally produced hormone primarily synthesized and secreted in the pineal gland. Melatonin regulates the body's sleep-wake cycles by interacting with the suprachiasmatic nucleus of the hypothalamus and the retina.

Estradiol and progesterone belong to a family of steroid hormones with complex actions. Estradiol-17β (E2), the predominant and most biologically active estrogen, is an 18 carbon (C-18) steroid with an aromatic A-ring. It is synthesized mainly by the ovary; however, other organs and tissues, including adipose tissue, the brain (neurons, astrocytes, and microglia), cells of the immune system, and bone, are thought to produce it as well. Progesterone is a C-21 steroid hormone, which is not only an active hormone in and of itself, but is also a precursor to estrogens.

Estrogens (estradiol, estriol, and estrone) are important hormones that directly and indirectly regulate the metabolism and function of bone and skeletal muscle via estrogen receptors.

Oxytocin is a nonapeptide consisting of a cyclic six amino-acid structure and a tail of three amino acids. It was originally known for its ability to induce milk ejection and to stimulate uterine contractions. More recently, oxytocin has been shown to stimulate social behaviors, and exert pain-relieving, anti-stress/anti-inflammatory and restorative effects

Plasma free metanephrines are commonly used for diagnosis of pheochromocytoma and paraganglioma (PPGLs).

Renin is an aspartyl protease released by the juxtaglomerular cells of the kidneys in response to perceived low blood pressure and renal perfusion. It plays an essential role in the rate-limiting step of the renin-angiotensin-aldosterone system (RAAS), responsible for the homeostasis of blood volume and mean arterial blood pressure.

Cortisol has a variety of effects on different functions throughout the body. It is the main glucocorticoid released from the zona fasciculata layer of the adrenal cortex. The hypothalamus-pituitary-adrenal axis regulates both production and secretion of cortisol. Cortisol, a steroid hormone, is synthesized from cholesterol. It is synthesized in the zona fasciculata layer of the adrenal cortex.