Sheldon's mother, while sometimes being warm and caring is most famously known for being a controlling religious fundamentalist

Leonard's mother is nearly as bad as Evelyn. She is emotionally distant, uncaring and also did experiments on Leonard when he was a child (maybe a pattern?)

Howard's mother of course represents the typical negative Jewish mother
stereotype while also being morbidly obese and physically revolting

Raj's mother is extremely controlling and doesn't show love to either Raj nor Priya

It isn't just an issue or pattern on TBBT but on Two and a Half Men also:
Evelyn of course is the most unmotherly figure you can imagine

Judith is neurotic and selfish and doesn't seem to care about Jake at all

Walden's mother used to do experiments on him when he was a child

Lindsay's mother is a two-faced FEMALE DOG

Chelsea's mother is a racist

Bertha as a mother seems uncaring and only speaks ill of her offspring