Shirley S. Wang (WSJ) reports:

"Much of the research in the field is focused on vitamin D. The receptor—the lock to which the vitamin D key binds—activates hair growth, rather than the vitamin itself, says Marie Demay, a professor of medicine at Harvard Medical School, who pioneered much of this work.
Biochemist Yuko Oda and a team at the VA Medical Center San Francisco and the University of California, San Francisco, recently found a molecule, called MED, that appears to suppress the actions of the receptor. In a study published in December in the Journal of Investigative Dermatology, they found that mice generated more hair after the gene that codes for MED in their skin was knocked out, suggesting a target for gene therapy.
Dr. Demay and colleagues last year found another molecule called LEF1 that also activates the vitamin D receptor, and can do so without the presence of vitamin D. The next step will be to demonstrate that activating the receptor in this way would actually produce hair, says Dr. Demay. If these molecules activate the vitamin D receptor, they change the "fate" of the cells into hair cells, Dr. Oda says. The work was published in the Journal of Biological Chemistry.
Researchers at the University of Tokyo recently added vitamin D supplements to the medium in which they were growing dermal papilla cells, hoping to spur more uncommitted stem cells to become active follicles.
In rats, the scientists found more stem cells were coaxed into becoming follicles when vitamin D was used in the final phase of growing the cells than those not treated, says Kotaro Yoshimura, a professor in the department of plastic surgery who was the senior author on the paper. In addition, more of those follicles matured to produce hair, raising the hope that this might lead to improved hair transplants in the future. The study appeared in the journal Stem Cells Translational Medicine.
Currently, hair transplants can only get single hair from one follicle "but we want to make 1,000 hairs from one follicle," one after the next, says Dr. Yoshimura. They are now teaming up with two other sets of researchers and planning a clinical trial.
A challenge for researchers is that vitamin D has many functions in the body, such as improving bone growth. Taking too much vitamin D can have negative side effects such as calcium accumulation in the blood causing weakness or kidney problems, according to the Mayo Clinic. So it is important that any potential treatment be finely targeted. "We're really aiming to manipulate vitamin D or vitamin D receptors only in the skin," Dr. Oda says."

Read the complete article at http://online.wsj.com/article/SB10000872396390443921504577643442954317340.html

--Results of this reasearch on vitamin D receptors in the skin and what it can actually do for patients with hair loss is, of course, many years off.  For today, those with male or female pattern baldness can seek the advice of a hair restoration physician who can provide medical treatments (like Minoxidil 82M, finasteride, bimatoprost/latisse) as well as minimally-invasive hair transplant surgery (NeoGraft FUE).  Seek treatments from doctors who routinely perform the procedures and evaluations on a regular basis... not a part-time or newbie physician. Congratulations to the International Society of Hair Restoration Surgery (ISHRS) for the mention in the article. --Dr. Alan Bauman,  Bauman Medical Group Hair Transplants and Hair Loss Treatments in Florida