Thymulin's Eight Trials Measure Zinc

The count

A census run against PubMed on 2026-09-02, across the two names the literature uses, returns 498 indexed records for thymulin, of which 226 carry the Humans subject heading, 8 the clinical-trial publication type, and 5 the randomized-controlled-trial type ^[1]. The publication-type filters were proved live in the same run: the control term aspirin returned 8,906 records under the clinical-trial filter and 6,115 under the randomized filter, the invalid tag clinicaltrial[pt] returned zero for that same control term, and a deliberately invalid record identifier errored ^[1].

Eight is a number a marketer can use and a reader can check, which is why it is worth checking. Eight is also small enough to itemize, so every one of the eight was retrieved and read rather than counted.

What the eight records are

Seven of the eight do not administer thymulin. They measure the concentration of the body's own thymulin as a readout of something else, almost always zinc status, because the molecule is biologically active only when bound to zinc and therefore makes a convenient marker for zinc sufficiency.

One is a trial of zinc supplementation in patients with Crohn's disease, which reported that zinc restored plasma concentrations of both zinc and thymulin ^[2]. Another is a trial of zinc supplementation in young rural Gambian children ^[3]. The remainder run along the same line: zinc supplementation in children with Down's syndrome, zinc as an adjunct to zidovudine therapy, a zinc-fortified skim milk, thymulin concentrations tracked against melatonin, and thymulin measured against prenatal and childhood exposures in adolescents ^[1].

The eighth record does administer something, and it is not thymulin. A 1989 double-blind pilot study tested nonathymulin — a synthetic analogue — in multiple sclerosis ^[4]. That is the whole of the administered human record indexed under these names: one pilot study, of a different molecule, in an unrelated field, thirty-seven years ago.

Why the count exists at all

This is not a search artifact to be tuned away. The searches are correct and the records genuinely concern thymulin; what they do not do is test it. The count exists because a molecule that serves as a biomarker accumulates trial-type records from every field that uses the marker, and a publication-type filter cannot distinguish a substance that was given from a substance that was measured.

No filter can make that distinction, which is the general lesson. A trial count is a count of publication types, and the only way to know whether the records administer the compound is to open them. This index therefore records, beside every small count it prints, whether the hits were read and what they were; the human trial record carries that column, and this row is the reason the column exists.

What is left of the claim

Thymulin is sold as research-use-only material on claims about immune function and thymic aging. The honest statement of its human record is that no indexed trial has administered it to a person, that a synthetic analogue has one 1989 pilot in an unrelated indication, and that everything else counted under the name is a measurement of endogenous concentration.

The regulatory record is correspondingly thin. The section 503A bulks list published May 14, 2026 files Thymulin acetate in Category 3, the category for substances nominated without adequate support to evaluate, and Drugs@FDA holds no approved product with thymulin as an active ingredient ^{[5, 6]}. The monograph carries the dated ledger, and Category 3 explains what that filing means.

Elsewhere in this index