Angularjs $http put request response NULL

Problem in sending data if i will append all parameters to form Data than some of will not updating.

$scope.updateHospital = function(){
            $scope.spList = []; 
            var selected = $("#lstSpe option:selected");
                var message = [];
                selected.each(function () {
                    message.push($(this).val());
                });

                message.forEach(function(entry){
                    $scope.spList.push($scope.id[entry]); 
                });

            var formdata = new FormData();
            console.log($scope.name+$scope.des+$scope.spList);//all three fields have correct value in it

            formdata.append("name",$scope.name);
            formdata.append("description",$scope.des);
            formdata.append("primarySpecialty",$scope.spList);



            $http({
            method : 'PUT',
            url    : 'url',               
            headers : {"authorization" : access_token,"Content-type":undefined},
            data   :   formdata
            })

if i append "spList" to my form data than "name" and "description" is not updating the value when i send only "name & description" it is working fine. from postman this is working fine with all three values.