What cause low testosterone, severe muscle wasting, 100lb wght loss, changes in color hair? now the spouse has suddenly died of tumor in her head?

Need medical attention: The compilation of the several symptoms are concerning. I am so sorry about the loss of your spouse. Low testosterone or hypogonadism can lead to muscle reduction. Large unexpected weight reduction is concerning about it hypermetabolic condition and a good medical valuation thorough history and physical exam most important.

Talk to your PCP: You need to talk to your pcp. The death of a spouse is unrelated except depression may be part of it.