programmatically retrieve Header component height - React Native

Using NativeBase, I added a Header component. Now, I want to programmatically retrieve the height of the header. How can I do this. The code for adding the Header is given below:

I tried using Dimensions.get('window') but it gives me the height of the entire view.

The code:

import React, {Component} from 'react-native';
import {Container, Header, Button, Title, Icon} from 'native-base';
​
export default class ThemeHeaderExample extends Component {
    render() {
        return (
                <Header>
                    <Button transparent />

                    <Title>Header</Title>

                </Header>
        );
    }
}