But like most peptides on the market, TB-500 has limited long term studies involving human use. Although I haven’t personally used TB-500 (I can’t, since I compete in WADA sanctioned sports like triathlon and obstacle course racing), from what I’ve seen and heard from bodybuilders and athletes using the peptide, the primary side effect is a temporary sense of lethargy. Also, some people report getting a head rush when injecting TB-500, but report this head rush goes away a few minutes after injecting.
Johansson, A., Westberg, L., Sandnabba, K., Jern, P., Salo, B., & Santtila, P. (2012). Associations between oxytocin receptor gene (OXTR) polymorphisms and self-reported aggressive behavior and anger: Interactions with alcohol consumption [Abstract]. Psychoneuroendocrinology 37(9), 1546-56. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/22421562
5-HTP can affect a brain chemical called serotonin. Dextromethorphan (Robitussin DM, others) can also affect serotonin. Taking 5-HTP along with dextromethorphan (Robitussin DM, others) might cause too much serotonin in the brain and serious side effects including heart problems, shivering, and anxiety. Do not take 5-HTP if you are taking dextromethorphan (Robitussin DM, and others).
Letdown reflex. In lactating (breastfeeding) mothers, oxytocin acts at the mammary glands, causing milk to be ‘let down’ into a collecting chamber, from where it can be extracted by compressing the areola and sucking at the nipple. Sucking by the infant at the nipple is relayed by spinal nerves to the hypothalamus. The stimulation causes neurons that make oxytocin to fire action potentials in intermittent bursts; these bursts result in the secretion of pulses of oxytocin from the neurosecretory nerve terminals of the pituitary gland.
The first time Ditzen and her colleagues did this experiment they found that for both men and women oxytocin improved communication and lowered cortisol, a stress hormone. But in a recent study published in Social Cognitive and Affective Neuroscience, Ditzen and her colleagues measured salivary alpha-amylase (sAA)—an enzyme tied specifically to social stress—and found that men and women responded differently. Women who got oxytocin showed a decrease in sAA whereas men showed an increase and reported feeling more intense emotions. Counterintuitively, these men were also better at communication during conflict: they smiled more, had more eye-contact and were more open about their feelings. These behaviors are essential for peaceful conflict resolution.
Jump up ^ Low TL, Hu SK, Goldstein AL (February 1981). "Complete amino acid sequence of bovine thymosin beta 4: a thymic hormone that induces terminal deoxynucleotidyl transferase activity in thymocyte populations". Proceedings of the National Academy of Sciences of the United States of America. 78 (2): 1162–6. Bibcode:1981PNAS...78.1162L. doi:10.1073/pnas.78.2.1162. PMC 319967. PMID 6940133.

^ Jump up to: a b Low TL, Hu SK, Goldstein AL (February 1981). "Complete amino acid sequence of bovine thymosin beta 4: a thymic hormone that induces terminal deoxynucleotidyl transferase activity in thymocyte populations". Proceedings of the National Academy of Sciences of the United States of America. 78 (2): 1162–6. Bibcode:1981PNAS...78.1162L. doi:10.1073/pnas.78.2.1162. PMC 319967. PMID 6940133.


When combined with antidepressants of the MAOI or SSRI class, very high parenteral doses of 5-HTP can cause acute serotonin syndrome in rats.[23][24] It is unclear if such findings have clinical relevance, as most drugs will cause serious adverse events or death in rodents at very high doses. In humans 5-HTP has never been clinically associated with serotonin syndrome, although 5-HTP can precipitate mania when added to an MAOI.[25]
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