When measuring testosterone levels, it is critical to determine the levels of both free and total testosterone to understand the cause of any observed symptoms of deficiency (Khosla et al 2008).
Because of difficulties with equipment standardization and inter-laboratory variability, it is recommended that physicians consistently use the same local laboratories and gain familiarity with the accuracy, precision and definition of normal values for the assays offered in their communities (Morales et al 2010).
Newman explains that medical disruptions involving prolactin, the hormone necessary to produce milk, have resulted in spontaneous lactation. Thorazine, a popular antipsychotic used in the mid-20th century, impacted the pituitary gland—the pea-size endocrine gland located near the base of the brain—often causing it to overproduce prolactin. If prolactin levels remained high, milk could follow. According to Newman, lactation is listed as a possible side effect of the heart medication digoxin. A pituitary tumor could also induce milk production: "It would be the same reason—increased prolactin levels&mdashin the one case drug-induced, in the other due to a tumor or some other sort of neurological problem."
In a 1995 article for Discover titled "Father's Milk," Pulitzer Prize-winning author and one-time physiologist Jared Diamond reconciles the nipple stimulation and hormone quandary, pointing out that such stimulation can release prolactin. He also notes that starvation—which inhibits the functioning of hormone-producing glands as well as the hormone-absorbing liver—can cause spontaneous lactation, as observed in survivors of Nazi concentration camps and Japanese POW camps in World War II. "The glands recover much faster than the liver when normal nutrition is resumed," he writes, "so hormone levels soar unchecked."
Males of many different mammalian species have the potential to lactate, although only one, the Dayak fruit bat of Southeast Asia, does so spontaneously. Diamond points out, however, that with the societal norm of fathers helping to rear their young, male milk production could actually be to our advantage, especially with all the career women trying to balance the demands of job and family. Why else would men still have nipples?
"Up until a certain age, boys and girls, as fetuses, are indistinguishable, really, so women retain some remnants of the vas deferens, which is the canal that sperm follows," Newman answers. "If you have no Y chromosome, then certain hormones are released that say, 'Okay, we'll set up this child's breast tissue to develop at puberty so that she will be able to produce milk.' Men didn't [secrete those hormones], so we don't usually have breast tissue."
"Actually a significant number of boys around the age of puberty do develop breasts," he continues, "so the tissue is there, but it regresses." In short, men may not have full-fledged breasts but they certainly can lactate, under extreme circumstances.
Many transgender men chose not to undergo hysterectomy, oopherectomy and/or gender affirming genital procedures.[19,21,22] For transgender men of reproductive age undergoing transition without hormones, or those whom have used testosterone and later discontinued it due to unwanted side effects such as balding, menses would be expected to be within standard reference ranges from 21-35 days between cycles with no inter-menstrual bleeding and lasting on average 2-6 days and ceasing on average at age 49. Variation from these ranges warrants further gynecological investigation.