U.S. federal regulators said Friday they were investigating products containing testosterone after recent studies suggested a higher risk of strokes and heart attacks in men being treated with the hormone.

The Food and Drug Administration stressed, however, that it has "not concluded that FDA-approved testosterone treatment increases the risk of stroke, heart attack or death."

French pharmaceutical giant Sanofi has said it is suing U.S. rival Eli Lilly in an American court for infringing four patents relating to its diabetes treatments.

The lawsuit, lodged in the state of Delaware, was triggered by Eli Lilly's notification last month that it plans to ask the U.S. Food and Drug Administration (FDA) for permission to put a new diabetes treatment on the market.

Uganda's government is planning to double expenditure on anti-retroviral drugs in an effort to reverse a worsening trend in HIV infections, a senior health official said Thursday.

The doctor in charge of the health ministry's AIDS control program, Alex Ario, told AFP that over the next year some 1.3 million people will have free access to ARVs, compared to the 600,000 currently being treated.

A new study finds that people in nations where the population is aging less swiftly, such as the U.S, are less likely to be worried about their old-age futures than those in parts of Europe and East Asia that are grappling with swiftly shrinking workforces and increasing pension costs.

The survey by the Pew Research Center covers 21 nations.

Brain scans may help identify children with learning difficulties much earlier by measuring their short-term memory capacity, according to a Swedish study published Wednesday.

The study by a team of researchers at Karolinska Institute, published in the Journal of Neuroscience, showed that it is possible to map the development of short-term memory capacity with Magnetic Resonance Imaging (MRI scans).

People who smoke or have lung cancer should think twice about taking vitamin supplements, according to a Swedish study Wednesday that showed certain antioxidants may make tumors grow faster.

Lab mice that already had cancer were given vitamin E and a drug called acetylcysteine, which sped the growth of their tumors and made them die faster than mice that did not ingest supplements.

Adult men with attention deficit hyperactivity disorder may avoid traffic accidents if they take their prescribed medication, said a Swedish study on Wednesday.

The study found that men with ADHD were 45 percent more likely to get into road crashes due to inattentiveness and impulsiveness than men without the disorder.

Doctors said Thursday they could treat peanut allergy by feeding children the very thing their bodies reject, so building tolerance that could save a life in case of accidential ingestion.

Small doses of peanut powder taken over several months seemed to induce tolerance in children with the potentially deadly allergy, a research team wrote Wednesday in The Lancet medical journal.

Obesity among U.S. children is largely established by kindergarten, a study said Wednesday, adding that nearly half of those obese at 14 already had the problem at age five.

The study published in the New England Journal of Medicine also showed that over 14 percent of children enter kindergarten overweight and are four times more likely than normal weight children to become obese by the eighth grade.

Scientists Wednesday reported a simple way to turn animal cells back to a youthful, neutral state, a feat hailed as a "game-changer" in the quest to grow transplant tissue in the lab.

The research, reported in the journal Nature, could be the third great advance in stem cells -- a futuristic field that aims to reverse Alzheimer's, cancer and other crippling or lethal diseases.