Dried tissue from animal glands — thymus, adrenal, thyroid, pituitary, spleen or pancreas — usually bovine or ovine, sold on the principle that a gland supports the corresponding human gland.
Glandulars rest on a nineteenth-century idea sometimes called organotherapy: that eating an organ supplies something specific to that organ in the person eating it. The physiology does not support it. Peptide hormones and tissue-specific proteins are digested to amino acids, and the amino acids are indistinguishable from those in any other protein. Where glandulars do have an effect, it is usually because they contain actual hormone — desiccated thyroid products have been found to contain thyroid hormone at pharmacologically meaningful levels, causing thyrotoxicosis in people who did not know they were taking a hormone. Beyond that, this is the supplement category where the bovine sourcing question is sharpest, because it involves precisely the lymphoid and neuroendocrine tissues that transmissible spongiform encephalopathy controls were written for.
None; hormone content is neither standardised nor usually measured, which is the central safety problem — a product without this marker may not resemble what was studied.
Regulation: Sold as dietary supplements in the US with no pre-market efficacy or safety review. Regulators have taken action over thyroid glandular products containing undeclared thyroid hormone, and several countries restrict or prohibit bovine glandular material on prion-control grounds. Thymus extracts were studied as licensed medicines in parts of Europe and are not approved in the US.
What the research used
The amounts, forms and durations published trials of Glandular extracts (thymus and others) actually administered.
These are the amounts published trials administered — not a recommendation, and not a dose to copy. Trial participants were screened, supervised and given a characterised preparation. What is in a retail bottle is frequently not what was studied, and the amount that suits one person is not general advice.
Studied for Common supplement use
100–1000 mg
Not enough
Dried glandular tissue, daily
What products contain. No dose can be considered established: there are no adequate trials, and the amount of active hormone in a given batch is unknown and unregulated.
This is general information about food, not medical advice. It cannot diagnose, treat or replace guidance from a clinician who knows your history.
When it was taken
Each window says whether a trial compared it against an alternative, or whether it is convention and pharmacology. Most timing advice is the second kind.
None of the timings below were directly compared in a trial. They reflect how the research happened to dose, or what the pharmacology implies — which is not the same as a timing being better.
🕐Any time
Not enough
No timing research exists for glandular preparations.
Timing was not directly compared. This reflects convention or how the compound behaves in the body, not a trial showing this window works better.
The evidence in depth
Best supported: Not enough
What each association actually rests on, and the papers behind it. A rating describes the state of the research, not how promising the supplement sounds. How we rate evidence.
Adrenal glandulars are sold for fatigue and "adrenal fatigue", a concept that systematic reviews have found no evidence to support as a clinical entity. There are no trials of adrenal glandulars for fatigue.
Not enough evidence. Not enough human research to say anything useful yet.
Thymus extracts were investigated in Europe decades ago with small and methodologically weak studies. There is no adequate modern evidence that oral thymus tissue affects immune function in people.
What may be going on: The premise is that thymic peptides survive digestion and act on the human thymus. Peptides are hydrolysed to amino acids in the gut, and no study has shown intact tissue-specific peptides entering the circulation.
Not enough evidence. Not enough human research to say anything useful yet.
Meta-analysis · The Cochrane database of systematic reviews · 2025 · PMID 40919695
Deep research mode adds each paper’s own conclusion and stated limitations.
Things to know
Interactions, contraindications and dose limits, most serious first. Concentrated extracts interact with medication in ways the whole plant does not, so this section carries more weight here than it does on a food page.
Worth knowing
Thyroid glandulars can contain real thyroid hormone
Interacts withLevothyroxine, antithyroid drugs
Analyses of thyroid glandular supplements have found meaningful amounts of thyroxine and triiodothyronine, and cases of thyrotoxicosis have followed their use — including in people taking them for fatigue with no thyroid diagnosis. An unmeasured dose of a hormone taken without monitoring is a genuinely dangerous arrangement, particularly alongside prescribed thyroid medication.
Worth knowing
BSE-era sourcing concerns
Glandulars use exactly the tissue types — thymus, spleen, lymphoid, neuroendocrine — that specified-risk-material rules were created to control after the BSE epidemic. Several countries restrict bovine glandular imports. Country of origin, herd traceability and documented controls are the minimum, and most products document none of it.
Worth knowing
The organotherapy premise is not physiology
Eating a gland does not deliver that gland's function. Tissue-specific proteins are digested like any other protein, and where a glandular does something it is because it contains hormone, not because of tissue affinity.
Avoid
Not appropriate in pregnancy, childhood or autoimmune disease
Unmeasured hormone content, unknown immunological activity and animal tissue sourcing make these unsuitable in pregnancy, in children and in anyone with autoimmune or endocrine disease under management.