Hilary Duff reveals she 'lost touch' with Hayden Panettiere as she remembers fellow child star after her death at 36

Hilary Duff paid tribute to Hayden Panettiere on Tuesday, touching on their past friendship as up-and-coming stars in Hollywood.

'Sweet Hayden,' the 38-year-old actress wrote in an Instagram post. 'Really tough hearing this news.'

The Lizzie McGuire star said: 'We lost touch through the years, but I will always remember you as so hardworking and effervescent, with that big, gorgeous smile.'

Duff went on: 'I remember staying up late, chatting and gossiping, and connecting because we were part of such a small sliver of people who actually understood the strange lot in life we were navigating.'

Panettiere died Sunday at age 36 after being found unresponsive at an apartment in Greenville, South Carolina, following a suspected overdose that caused cardiac arrest. 

The Daily Mail has reached out to representatives for Duff for further comment on the story but has yet to hear back.

She said that at the time, they were 'so young, with no real idea how to make sense of any of it.'

Both Duff and Panettiere were prominent child stars around the same timeframe: Duff starred on Lizzie McGuire beginning in 2001, and in films such as 2003's Cheaper by the Dozen and 2004's A Cinderella Story.

Panettiere established herself with roles on soaps such as One Life to Live and Guiding Light, and in the 2000 film Remember the Titans.

Duff wrapped up her somber post in saying, 'I so deeply wish this wasn't the end for you.

'Sending a heart full of love to your family, the many people you impacted and everyone who loved you. Rest easy.'

Duff was one of a number of Panettiere's peers to publicly mourn the star following news of her tragic death.

Actress Alexa PenaVega, 37, referenced two other notable stars who died prematurely earlier this year, Michelle Trachtenberg this past February at 39, and Daveigh Chase in June at 35, in her memorial to Panettiere.

'These aren't just names from my childhood,' PenaVega said. 'They're girls I grew up alongside, sharing a world that was exciting and also incredibly hard. 

'We were kids navigating something so big, and not everyone had the foundation or support they deserved.'

PenaVega added: 'Today, I'm grieving and holding their families close in my prayers and thinking of everyone still fighting battles we can't see. Hug your people close today.'

Solange Knowles, 40, mourned her late costar in Bring It On: All or Nothing in writing, 'Rest in peace Hayden ... in peace, because you are so deserving of it ... 

'We had so many parallels in our lives, and the world watched u so courageously live in your radical truth telling your story. We watched your endless quest for vulnerability, and healing.'

Paris Hilton, 45, described Panettiere as 'so talented, strong, kind and full of so much love and light' in a social media tribute, adding, 'I’ll always cherish our friendship, all the memories we shared, and the special moments we had together.'

Emma Roberts, 35, said: 'Rest in peace my sweet friend. You are so loved and you will be forever missed.'

Panettiere's passing was announced Sunday by her father Skip Panettiere, who said in a statement: 'It is with profound sadness that we share the tragic passing of our beloved Hayden.

'She was an incredible light and a force of nature who brought immeasurable love and joy to all who knew her - and to the millions who watched her onscreen. We ask for privacy as our family takes time to process this unimaginable loss.'

Authorities in Greenville, South Carolina, subsequently said that officials responded to an apartment in the area after receiving a report of an 'unresponsive female' via a possible 'drug overdose,' subsequently determined to be Panettiere.

Officials, who attempted lifesaving measures prior to declaring the actress deceased, said that no signs of trauma or foul play were evident in their probe into the Panettiere's death, which remains ongoing.