Why does my function not work when called?

Currently doing a BMR calculator for practice but I can't seem to get the function to work. Trying to use the male bmr formula if the male radio button is checked, but no alert appears.

<script>
    if(gender==male){
        function bmr(weight, height, age) {
            var malebmr = (66 + (13.7 * weight) + (5 * height) - (6.8 * age));
            return malebmr;
        }
    else {
        function bmr(weight, height, age) {
            var femalebmr = (655 + (9.5 * weight) + (1.8 * height) - (4.7 * age));
            return femalebmr;
        }
    }
    }

    function calculatebmr() {       
        alert(bmr(parseFloat(document.bmiform.weight.value),
        parseFloat(document.bmiform.height.value),
        parseFloat(document.bmiform.age.value)));
    }

</script>    

<fieldset data-role="controlgroup" data-type="horizontal">
    <legend>Gender</legend>
    <label for="male">Male</label>
    <input type="radio" name="gender" value="male" id="male" checked>
    <label for="female">Female</label>
    <input type="radio" name="gender" value="female" id="female">
</fieldset>
<input type="button" value="Calculate"
onclick="calculatebmr()">