A palindrome is a sequence of characters which reads the same backward or forward, e.g "rotator", "madam" and "1221". Write a function isPalindrome which accepts one input string and returns true if the string is a palindrome and false otherwise. Your function should ignore letter case: "madam" and "Madam" are both palindromes. The function should return the desired output regardless of the input string size. You are required to use the programming method (loops, conditional statements) to check if the input string is a palindrome. Your solution cannot use any Matlab built-in function that has either "str", "eval", "flip" or "printf" in it.

Here's an example of a function call:

isPalindrome('1221')

ans = 1