<unk>  is a biochemical phenomenon observed in a wide variety of cell and tissue types, in which chemical products are secreted in a regular temporal pattern. The most common cellular products observed to be released in this manner are intercellular signaling molecules such as hormones or neurotransmitters. Examples of hormones that are secreted<unk> ly include insulin, thyrotropin, TRH, gonadotropin-releasing hormone (GnRH) and growth hormone (GH). In the nervous system,<unk> ty is observed in oscillatory activity from central pattern generators. In the heart, pacemakers are able to work and secrete in a<unk>  manner. A<unk>  pattern is critical to the function of many hormones in order to maintain the delicate homeostatic balance necessary for essential life processes, such as development and reproduction. Variations of the concentration in a certain frequency can be critical to hormone function, as evidenced by the case of GnRH agonists, which cause functional inhibition of the receptor for GnRH due to profound downregulation in response to constant (tonic) stimulation.<unk> ty may function to sensitize target tissues to the hormone of interest and upregulate receptors, leading to improved responses. This heightened response may have served to improve the animal's fitness in its environment and promote its evolutionary retention.<unk>  in its various forms is observed in: *Hypothalamic-Pituitary-Gonadal axis (HPG) related hormones *Glucocorticoids *Insulin *Growth Hormone *Parathyroid hormone
Pulsatile secretion
Insensible perspiration
Hypoallergenic
Overeating
Sensitive skin
Tenderness 
Pain out of proportion
Mucopurulent discharge