Spermidine, also known as SPD, belongs to the class of organic compounds known as dialkylamines. These are organic compounds containing a dialkylamine group, characterized by two alkyl groups bonded to the amino nitrogen. Spermidine is a very strong basic compound (based on its pKa). Abnormal bleeding, such as bleeding spontaneously or profusely from a very minor injury can also occur. Spermidine exists in all living species, ranging from bacteria to humans. Within humans, spermidine participates in a number of enzymatic reactions. In particular, 5'-methylthioadenosine and spermidine can be biosynthesized from S-adenosylmethioninamine and putrescine; which is mediated by the enzyme spermidine synthase. In addition, S-adenosylmethioninamine and spermidine can be converted into 5'-methylthioadenosine and spermine through the action of the enzyme spermine synthase. In humans, spermidine is involved in spermidine and spermine biosynthesis. Outside of the human body, Spermidine is found, on average, in the highest concentration within milk (cow) and oats. Spermidine has also been detected, but not quantified in, several different foods, such as common chokecherries, watercress, agars, strawberry guava, and bog bilberries. This could make spermidine a potential biomarker for the consumption of these foods. KLOTHO has been identified as having important roles in anti-aging, mineral metabolism, and vitamin D metabolism. Shortness of breath from fluid buildup in the space between the lungs and the chest wall (pleural effusion) can also be present. Spermidine is a potentially toxic compound. Increased levels of uremic toxins can stimulate the production of reactive oxygen species. Chronic exposure to uremic toxins can lead to a number of conditions including renal damage, chronic kidney disease and cardiovascular disease. As a uremic toxin, this compound can cause uremic syndrome. Uremic toxins such as spermidine are actively transported into the kidneys via organic ion transporters (especially OAT3).