Babies born younger? Scientists discover thyroid hormones can lengthen lifespan before birth

TURKU, Finland — It may sound like something Yogi Berra might say, but you’re never as young as the day you were born. Scientists in Finland however are trying to change this fact. Their study finds certain hormones in a pregnant mother’s body can actually rewind the biological clock. Simply put, babies can be born younger, thanks to a process that may someday lengthen lifespans.

A team funded by the Academy of Finland and the Turku Collegium for Science and Medicine has discovered that injecting maternal thyroid hormones into embryos creates longer telomeres. Telomeres are the protective caps on the end of chromosomes. Although they don’t carry genetic information, telomeres play a vital role in keeping DNA stable. Scientists measure these end caps to calculate a subject’s biological age.

Telomere strands normally get shorter as a human or animal ages; making them a good predictor of disease and mortality risks. When pregnant mothers pass on stress hormones to their child, this can also shorten telomeres before the baby is even born. In this experiment, scientists injected the eggs of birds to see the impact of adding thyroid hormones.

“The telomere biology of humans is closer to the telomere biology of birds than those of traditional laboratory models. In both human and birds, telomere length is measured in a minimally-invasive way from small blood samples,” says Collegium researcher Antoine Stier in a university release.

An egg-citing surprise for longevity seekers

Study authors say they had expected the chicks coming from hormone-injected eggs to have shorter telomeres. The final results revealed the surprising benefit of adding a mother’s thyroid hormones to their development; literally adding years onto a baby’s life.

“Based on the natural decline of telomere length observed with age in the same collared flycatcher population, we estimated that chicks hatching from thyroid hormones injected eggs were approximately 4 years ‘younger at birth’ than chicks hatched from control eggs,” Collegium researcher Suvi Ruuskanen explains.

Researchers say they’re not sure why the hormones are lengthening telomeres. The team theorizes prenatal thyroid hormones play a role in setting a baby’s “biological age” when they’re born.

“Considering the interest and controversies surrounding gene therapy trials in humans to elongate telomeres as an anti-ageing therapy, this discovery opens potential avenues to better understand the influence of telomere elongation in animal models,” Stier adds.

The study appears in the journal Biology Letters.