A mother who thought her baby was "depressed" has discovered his "grumpy behaviour" was due to a hormone deficiency.
Miranda Jones, 47, said her son Caspar spent his first year crying, clinging and looking upset.
However it wasn't until she measured him and realised he was smaller than his other siblings, she decided to see a specialist.
Caspar, now three, was diagnosed with growth hormone deficiency (GHD) at 18 months and now has daily hormone injections.
Jones said, according to the Mail Online: "I honestly believed he had depression but after he began his treatment, it was like a light had been switched on.
"Within a day, he was evidently livelier and more chatty. There's such a positive vibe in our house now."
After seeing their GP, the family decided to see a private endocrinologist, who diagnosed Caspar.
Jones said her son, who has undergone an "amazing transformation", receives Somatropin growth hormone injections.
Although prior to the injections Caspar wouldn't engage with other babies or his siblings, Jones said as soon as he began treatment, it was like a light had been switched on in his head.
The mother said she wanted to speak out about her son's story to make other parents aware of this symptom of GHD.
According to GOSH, GHD is produced by glands located in the brain.
The main symptom is that growth slows down or stops, but they advised it can be suspected through routine monitoring using growth charts or it may become more obvious when a child starts nursery or school and is much shorter than other children in the class.
Other telltale signs of Caspar's condition according to his mum included him not being able to sit up unaided until his first birthday, and not crawling, laughing or beginning to talk.
Jones said Caspar's mood would affect the whole family on days out, which prevented them all spending time together.
She added: "He was just a baby but he was so deeply sad that it rubbed off on all of us. I didn't want to go out and have to try and explain why he didn't want to engage with anyone."
Jones said, despite the daily injections, Caspar is "unphased" by the treatment.