load-(page_hook) action-hook . WP 2.1.0

Fires before a particular screen is loaded.

The load-* hook fires in a number of contexts. This hook is for plugin screens where a callback is provided when the screen is registered.

The dynamic portion of the hook name, $page_hook, refers to a mixture of plugin page information including:

The page type. If the plugin page is registered as a submenu page, such as for Settings, the page type would be 'settings'. Otherwise the type is 'toplevel'.
A separator of '_page_'.
The plugin basename minus the file extension.

Together, the three parts form the $page_hook. Citing the example above, the hook name used would be 'load-settings_page_pluginbasename'.

add_action( 'load-(page_hook)', 'action_function_name_5499' );
function action_function_name_5499(){
	// action...
}

In file: /wp-admin/admin.php

load-(page_hook)

do_action( "load-{$page_hook}" );

add_action( "load-$page", array( $this, 'admin_load' ) );

add_action( "load-$page", array( $this, 'take_action' ), 49 );

add_action( "load-$page", array( $this, 'handle_upload' ), 49 );

add_action( 'load-plugins.php', 'wp_plugin_update_rows', 20 ); // After wp_update_plugins() is called.

add_action( 'load-themes.php', 'wp_theme_update_rows', 20 ); // After wp_update_themes() is called.

add_action( 'load-tools_page_export_personal_data', '_wp_privacy_requests_screen_options' );

add_action( 'load-tools_page_remove_personal_data', '_wp_privacy_requests_screen_options' );

add_action( 'load-plugins.php', 'wp_update_plugins' );

add_action( 'load-update.php', 'wp_update_plugins' );

add_action( 'load-update-core.php', 'wp_update_plugins' );

add_action( 'load-themes.php', 'wp_update_themes' );

add_action( 'load-update.php', 'wp_update_themes' );

add_action( 'load-update-core.php', 'wp_update_themes' );