Published: February 15, 2020
Updated: November 23, 2022
Last year physician Eugene Gu tweeted that pain associated with circumcision causes some babies to go into "mental shock." There is no support for such a diagnosis, and Gu's controversial background makes it reckless that anyone would cite him as a medical authority.
Shock is a critical medical condition that is brought about by a sudden drop in blood flow throughout the body. The circulatory system fails to maintain adequate blood flow, sharply curtailing the delivery of oxygen and nutrients to vital organs. Signs and symptoms of shock include low blood pressure; over-breathing; a weak, rapid pulse; cold, clammy, grayish-blueish skin; decreased urine flow; and a sense of great anxiety and foreboding. 
The term "mental shock" can be applied to someone who has psychological anguish or discord, which could occur in cases of psychological disorders or severe depression. Mental shock implies inadequate perforation of the brain tissue. Typically a patient with this condition would be severely dehydrated or would have bled out. A newborn wouldn’t fit this criteria in the slightest, and mental shock is not caused by a physical injury.
"Neurogenic shock" is another type of shock that has been falsely attributed to circumcision. Neurogenic shock may occur after damage to the central nervous system, such as a traumatic brain injury or injury to the spinal cord. 
A lawsuit has been filed in a case involving a boy who suffered irreversible brain damage following a 2017 circumcision at a hospital in Portage La Prairie, a small city in Manitoba, Canada. Despite the boy showing signs of uncontrolled bleeding, medical staff sent the family home three times without any change in treatment. The parents, who weren't fluent in English, had trouble explaining that their son had bled all day. When the child became pale and started having trouble breathing, the family returned again. This time the patient was airlifted to a hospital in Winnipeg, where he was treated for "hemorrhagic shock, which occurs when the body starts to shut down due to blood loss."  It appears as if shock occurred because medical professionals negligently failed to treat the blood loss, not because of pain or psychological anguish.
At any rate, the notion that all babies go into shock during a (fully numbed) circumcision is ridiculous. It’s absurd to argue that most doctors and nurses either can't tell when their patient is actively dying, or conspire to lie about it to parents.
Eugene Gu is a controversial physician with a notorious history in both his professional and personal lives. In 2015, he gained national prominence when he was subpoenaed to appear before the U.S. Congress because his research group used tissue from aborted fetuses to conduct experiments. 
Vanderbilt University Medical Center placed Gu on probation in 2017 - after three years of a surgical residency. The university released him in 2018. In its decision the university cited a "lack of sufficient improvement in performance and conduct". A letter from VUMC stated that the "significant areas of concern [were] in patient care, communication, and medical knowledge."  Consequently Gu does not have a medical license.
Back in 2011 Gu's ex-wife accused him of domestic violence. Shortly after his release from VUMC a former girlfriend accused him of sexual harassment, claiming that he had become too aggressive on a date. She also accused him of using a sock-puppet account - @MaryLauryMD - to pose as a female doctor infatuated with himself.
"Mary posted pictures that were actually Gu’s, and posted things about Vanderbilt that no one other than Gu would have known. The hospital where Mary claimed she worked didn’t list a doctor under her name. When Allison finally tweeted at Gu to stop tweeting as Mary, the account was immediately deleted." 
Gu claimed that his ex-girlfriend had harassed him, but he admitted to using the sock-puppet account.  When the allegations of domestic violence came to light, other physicians reconsidered their earlier support for Gu. Some accused him of creating additional aliases whose sole purpose was to defend the embattled physician. 
Several stories involving brutal Black-on-Asian attacks became national news in March 2021. Gu responded to the pattern of inter-ethnic violence by blaming - incredibly - a racist “system of White supremacy.” 
Gu follows in the footsteps of intactivist icon Paul Fleiss, the osteopath-turned-pediatrician who was convicted of bank fraud and money laundering in support of his daughter Heidi Fleiss, a.k.a. the Hollywood Madam. As we documented in 2018, Fleiss provided questionable medical advice, and he was disciplined by medical authorities for his role in the death of a 3 1/2 year-old girl.  Like Fleiss, Gu has admitted to acts of deception. Unlike Fleiss, he hasn't played a role in anyone's death. At least not yet.
 Eugene Gu; Twitter post; January 11, 2019; 11:54 AM
 William C. Shiel, Jr., MD; "Medical Definition of Shock"; MedicineNet; Reviewed December 27, 2018
 Melissa Conrad Stöppler, MD; "Medical Definition of Neurogenic Shock"; MedicineNet
 Rachel Bergen; "Baby who bled for hours after circumcision was sent home from ER twice, suffered brain damage: lawsuit"; CBC News; July 3, 2022  Ankita Rao; "Who is Eugene Gu?' Vice; July 12, 2018
 Ben Leonard; "VUMC does not renew contract of Duke Med alum who kneeled against white supremacy"; June 1, 2018
 "Dr. Eugene Gu Accused of Sexual Assault and ‘Tormenting’ Ex-Girlfriend on Twitter"; NextShark; July 12, 2018
 Laura Yan; "The strange case of Eugene Gu"; The Verge; March 5, 2019  Eugene Gu tweet; March 29, 2021 - 9:29 PM (PDT). “Black on Asian crimes only occur because of our system of white supremacy that strips African Americans of their economic opportunities while taking respect and dignity away from Asian Americans. Also, white people in power are experts at dividing and conquering to stay in power.”
 "The intactivist hero who committed bank fraud and money laundering for the Hollywood Madam"; Circumcision Choice; January 16, 2018