The great-grandmother opened her birthday mesage from the Queen with her family around her.
But Mrs Porteous was modest about her birthday celebration, saying the secret to a long life is: "Pure good luck".
The 100-year-old, who still lives in her own home, in Coatbridge, said: "I'm not sure I want to think about how old I am but reaching 100 has been down to pure good luck.
"That and walking - I have always walked everywhere and tried to stay active."
Mrs Porteous was married in 1942 to Tom, who served in the RAF during the Second World War.
She said she remembered clearly the outbreak of war as she was singing in her church choir when the minister interupted the service to announce the news.
As a young woman Mrs Porteous sang in the choir of Wellington Church, Hillhead, taking two trams - even during the blackouts - to make sure she never missed a service.
Until the late 1970s she worked as a piano and singing teacher before giving up work to care for her husband, who died in 1982.
She is mum to Kath Roy, 69, and Tom, 66, and has four grandchildren and nine great-grandchildren.
Tom, a banker, said: "She has been a very special mum to Kath and I.
"She is just a truly decent person and a wonderful mother and grandmother."