Hormone (amines and peptide or protein hormones) are water-soluble and act on the surface of target cells via second messengers; steroid hormones, being lipid-soluble, move through the plasma membranes of target cells (both cytoplasmic and nuclear) to act within their nuclei. Hormone secretion may occur in many tissues. Endocrine glands are the cardinal example, but specialized cells in various other organs also secrete hormones. Hormone secretion occurs in response to specific biochemical signals from a wide range of regulatory systems. For instance, serum calcium concentration affects parathyroid hormone synthesis; blood sugar (serum glucose concentration) affects insulin synthesis; and because the outputs
Blood glucose monitoring to fluorescent detection, via measurement of viscosity. Investigation of affinity-based sensors has shown that encapsulation by body tissue does not cause a drift of the sensor signal, but only a time lag of the signal compared to the direct measurement in blood. Some new technologies to monitor blood glucose levels will not require access to blood to read the glucose level. Non-invasive technologies include near IR detection, ultrasound<ref name="Diabetes U/S SMBG"></ref> and dielectric spectroscopy. These may free the person with diabetes from finger sticks to supply the drop of blood for blood glucose analysis. Most of the non-invasive methods under