What Changed in the Teenagers' Bloodwork

The STEP TEENS trial established that semaglutide reduces BMI in adolescents. This follow-up analysis asked what else moved, and the answer is: nearly everything measurable — insulin resistance down 35%, liver enzymes down 18%, cholesterol and triglycerides improved.^[1] All of it is bloodwork. In a fourteen-year-old, the outcomes those markers stand in for are four decades away. For the weight results themselves and what a parent should ask about them, see GLP-1 drugs in teenagers.

What was found

The analysis covered 193 participants aged 12 to under 18 with obesity and without type 2 diabetes — 129 given weekly semaglutide 2.4 mg and 64 given placebo, over 68 weeks.

The liver result is the one that is not decades away

Most of that table describes risk accumulating toward events in middle age. ALT is different. Fatty liver disease is now the most common chronic liver condition in children, it is driven by exactly this metabolic picture, and elevated ALT is how it is usually first noticed.

A 17.9% fall against 3.3% on placebo is therefore not a marker for a distant outcome. It is a measure of something a substantial share of these teenagers plausibly already had, moving in the right direction now. Of everything in the analysis, it is the finding with the shortest distance between the number and a real condition.

Why the rest needs holding lightly

The general problem — markers moving correctly while patients do worse — has bitten cardiology more than once, and is set out in a biomarker is not an outcome. Nothing here suggests that is happening. The point is that improved adolescent bloodwork is a promising sign and not a demonstrated reduction in lifetime disease.

Two structural caveats belong with the numbers. This is a secondary analysis of a trial designed and powered to measure BMI, so these endpoints are being asked of data collected for another purpose. And the randomization ran two-to-one, leaving only 64 people on placebo — a small comparison group for a nine-row table.

One comparison in the paper that is not randomized

The analysis also reports that participants whose BMI fell by 20% or more had greater improvements than those whose BMI fell less. That reads like a dose-response relationship, which would strengthen the case considerably. It is not one.

It is a reasonable thing to report and an easy thing to over-read. A genuine dose-response would compare randomly assigned doses, not self-selected outcomes.

What is still unknown

• Long-term safety in a growing body. Sixty-eight weeks is the evidence base. Puberty, bone accrual and final adult height are not addressed by it.
• What happens on stopping — and adolescence is not a period anyone plans to take a medication through indefinitely without knowing that.
• Whether any of these markers translate into fewer events, which no trial in this age group can answer.
• Effects on eating behavior and body image during adolescence, which this analysis did not measure.

None of which argues against the drug in adolescents. It argues for describing what is known at the size it is known.