admin.py

from django.contrib import admin
from .models import Perfil
from django.contrib.auth.models import User
from django.contrib.auth.admin import UserAdmin as BaseUserAdmin
# Register your models here.

class PerfilInline(admin.StackedInline):
    model = Perfil
    can_delete = False
    verbose_name_plural = 'perfil'


class UserAdmin(BaseUserAdmin):
    inlines = (PerfilInline, )


admin.site.unregister(User)
admin.site.register(User, UserAdmin)

models.py

from django.db import models
from django.contrib.auth.models import User
from django.dispatch import receiver
from django.db.models.signals import post_save

class Perfil(models.Model):
    user = models.OneToOneField(User, on_delete=models.CASCADE)
    idade = models.IntegerField(blank=True, default=0)


@receiver(post_save, sender=User)
def criar_perfil(sender, instance, created, **kwargs):
    if created:
        Perfil.objects.create(user=instance)


@receiver(post_save, sender=User)
def salvar_perfil(sender, instance, **kwargs):
    instance.perfil.save()

views.py

from django.shortcuts import render
from django.contrib.auth.models import User
from django.http import HttpResponse

# Create your views here.
def update(request):
    usuario = request.POST['usuario']
    email = request.POST['email']
    senha = request.POST['senha']
    idade = request.POST['idade']
    novoUsuario = User.objects.create_user(username=usuario,
                                               email=email,
                                               password=senha)
    novoUsuario.save()
    novoUsuario.perfil.idade = idade
    novoUsuario.save()
    return HttpResponse("Cadastrado com sucesso.", content_type="text/plain")