Puberty hormone levels flagged future infertility in male childhood-cancer survivors

More children survive cancer than ever, and that success has shifted attention to the long shadow treatment can cast — including fertility. Chemotherapy and radiotherapy can damage the testes, but the damage is uneven: it depends on the drugs, the dose, and whether the radiation field included the testes. Knowing early which boys are headed for impaired fertility would let clinicians counsel families and, where possible, preserve options before it is too late. A cohort study published in JAMA Network Open on 9 October asks whether hormone levels measured during puberty carry that signal [s1].

What was done

Researchers at Helsinki Children's Hospital assembled a cohort of male childhood-cancer survivors who had been diagnosed under the age of 17 between 1964 and 2000, and for whom at least one reproductive hormone measurement was available (measured between 1982 and 2017) [s1]. In all, 221 survivors were included, with a median age at diagnosis of 6.0 years (interquartile range 3.2 to 11.7) [s1].

The exposures of interest were the two testis-toxic treatment types: alkylating chemotherapy, quantified as a cyclophosphamide equivalent dose (CED, a way of putting different alkylating drugs on one scale), and testicular radiotherapy [s1]. Serum follicle-stimulating hormone (FSH), luteinising hormone (LH), and testosterone were collected at two-year intervals between ages 12 and 18 and again at age 20 or older, and converted to age-specific z-scores so that levels could be compared across ages [s1]. FSH is produced by the pituitary and rises when the testis's sperm-producing (Sertoli cell) compartment is failing, which is why it serves as an early marker.

What the hormones showed

FSH tracked radiotherapy dose. Elevated FSH z-scores appeared from age 12 in boys who had received more than 1 gray of testicular radiotherapy [s1].

Alkylating chemotherapy showed a dose-response too. At age 18, boys who had received less than 4 g/m² CED had a median FSH z-score of 0.1 (IQR −1.2 to 1.2) — essentially normal. Those who received 4 to less than 12 g/m² had a median of 1.4 (IQR 0.5 to 2.6; P = .04), and those who received 12 g/m² or more a median of 1.6 (IQR 0.7 to 2.5; P = .007) [s1].

The crucial difference emerged later, in whether that elevation recovered. By age 20 or older, boys in the middle chemotherapy group had largely normalised — a median FSH z-score of 0.7 (IQR −0.6 to 1.7) — but the highest-dose group had not (median 1.7, IQR 0.9 to 2.5) [s1]. Radiotherapy damage, by contrast, persisted into adulthood [s1].

The predictive signal

The study's most clinically pointed finding is that the peak FSH during mid-puberty predicted the hardest outcome. The highest FSH z-score at ages 14 to 16 was associated with azoospermia — the absence of sperm — in adulthood. An optimal threshold corresponded to an FSH of 11.2 IU/L at age 14 and 12.5 IU/L at age 16, with an area under the curve of 0.87, which indicates good discrimination [s1].

Not everything was damaged equally. Elevated LH z-scores — a marker of the testosterone-producing Leydig cell compartment — appeared from age 12 only in boys who received more than 14 gray of radiotherapy, and high chemotherapy dose was not associated with impaired Leydig cell function [s1]. The authors read this as the Sertoli cell–germ cell compartment being more sensitive than the Leydig cells, meaning sperm production is more vulnerable than hormone production [s1].

How to read it

This is a single-centre cohort, and its reach back to diagnoses from 1964 means many survivors were treated with older protocols; treatment and supportive care have changed since. As an observational study it describes associations, not guarantees — a boy with a high pubertal FSH is at raised risk, not certain, of adult infertility. And azoospermia on a hormone proxy is not the whole fertility story, since sperm can sometimes be retrieved surgically even when counts in semen are absent.

Why it matters

Fertility counselling for childhood-cancer survivors has often waited until adulthood, when options narrow. This study suggests the information needed to flag high risk is already present during puberty, in routine hormone measurements, and that the pattern differs by treatment: radiotherapy effects that stay, chemotherapy effects that frequently recover [s1]. That is the kind of detail that lets counselling be both earlier and more specific.

This article is informational and does not constitute medical advice.