I agree on SIBO causing a shit load of issues but question is why does SIBO occur for some and not for others. My wild guess would be that those with slow gut transmit time (sluggish gut) will experience SIBO as a result. Normally, bacteria should not be found in large numbers in small intestines and there is a valve that separates large and small intestines.
Now back to slow gut transmit time. It is widely established that gut contractions/movements are governed by neurotransmitter Serotonin, which 90% of it is found in the gut. Thyroid gland also has a role in the gut. Basically, lower Serotonin and hypothyroidism are two key things that may cause slower than usual gut motility and therefore higher likelihood for SIBO. Serotonin is primarily governed by Estradiol.
Check this excerpt from NCBI:
“…Estrogen receptors and serotonin receptors coexist in cells in a wide variety of tissues, and this critical review of the literature suggests that many of E2’s effects may be mediated by changes in the actions of serotonin (5HT). Serotonin is usually considered to be a neurotransmitter, but surprisingly, only 1% of serotonin in the human body is found in the CNS [[4]]. The remaining 99% is found in other tissues, primarily plasma, the gastro-intestinal tract, and immune tissues, where serotonin acts as a hormone regulating various physiological functions including vasodilation[[5], recruitment of immune cells [[7], gastro-intestinal motility,[[10] and initiation of uterine contraction [[11].
E2 coontros the rate-limiting step in synthesis of serotonin from tryptophan), increasing the concentrations of Serotonin…”
In light of the above, one most have healthy E2 level for optimal gut function. E2 is created from Testosterone conversion so one must raise Testosterone first and achieve ideal T:E2 ratio in the range of 15-25. Ideal E2 level for most men is 22 pg/mL to 30 pg/ml.