Katacalcin
The piece of the calcitonin precursor released alongside calcitonin, once proposed as a hormone and studied as a thyroid cancer marker
Katacalcin is the 21-residue tail of preprocalcitonin, the protein thyroid C cells cut to make calcitonin. It was predicted from the gene in 1983, then found in blood, where it rises with calcitonin after calcium and is greatly raised in medullary thyroid carcinoma. Its first describers called it a calcium-lowering hormone, but no such action has been shown in people. It has only ever been measured, never given.
No established human dose Details ↓
Recommended Dosing
No established human dose
No study read has given katacalcin to a person. Every human study on this page measures it: in blood the body has released, in tissue sections, in milk and in seminal fluid.
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What is it?
Katacalcin is a 21-amino-acid peptide cut from the same precursor as calcitonin. The calcitonin gene's thyroid message codes for a single chain, preprocalcitonin, that holds an N-terminal piece, then calcitonin, then katacalcin at the far end. When the chain is processed in the C cells of the thyroid, calcitonin and katacalcin are split off and stored together. In UniProt's record of the human precursor (P01258), katacalcin occupies residues 121 to 141. In the older papers it is also called PDN-21 or the carboxyl-terminal flanking peptide of calcitonin.
It was found in 1983 the way several peptides of that decade were: by reading a cloned gene. The calcitonin message predicted a stretch of 21 residues beyond calcitonin that nobody had isolated, so researchers made it synthetically, raised antibodies against it and went looking. Those antibodies found it in the same thyroid C cells as calcitonin, normal and cancerous, adult and fetal. Measured in blood, it was present in every healthy volunteer tested and in roughly the same molar amount as calcitonin.
The first paper presented it as a second calcium-lowering hormone, but that role has not been shown. The abstracts read do not report a calcium effect of katacalcin in people, a 1989 study in children noted that its actions were still unknown, and as late as 2002 a laboratory group wrote that its biological role was unknown. In mice it did not change thyroid hormone output on its own. The one clear action reported in the abstracts read is in a dish: it drew human blood monocytes toward it through a cyclic AMP and protein kinase A pathway, at extremely low concentrations.
What katacalcin does reliably is travel with calcitonin. In healthy adults a calcium infusion raises both peptides within minutes, and the extracted forms correlate almost perfectly mole for mole. Men have higher resting levels and larger responses than women in most of the studies, and older women the lowest. Pentagastrin, a stimulus that raises calcitonin in people with C-cell disease, raised katacalcin little or not at all in healthy people. Levels were normal in chronic high calcium from overactive parathyroid glands, in girls with Turner syndrome and osteoporosis, and in women before and after removal of the ovaries.
That close tracking made katacalcin a candidate tumour marker for medullary thyroid carcinoma, the cancer of the C cells. Through the 1980s and early 1990s several groups measured it in patients and found it raised in nearly all of them, correlated with calcitonin at r = 0.98 to 0.99, stimulated by pentagastrin and calcium, and useful in sampling veins to locate tumours. One group judged it equivalent to calcitonin, and slightly more sensitive in a few patients with borderline results. A study of families with the inherited MEN-2 syndrome found the opposite edge: calcitonin rose more than katacalcin in early C-cell disease. In a large lung cancer series it was raised more often than calcitonin and added information to the standard markers. Calcitonin itself has its own entry; those studies of calcitonin are carded there.
Katacalcin turns up outside the thyroid too. Immunostaining found it with calcitonin and CGRP in endocrine-type cells of the prostate and urethra. Milk and seminal fluid contain large amounts of calcitonin-type material, but most of it is larger precursor forms rather than free katacalcin. Inside a thyroid tumour the peptide is also trimmed from its end into shorter pieces.
One distinction matters for readers who meet the name in infection medicine. Procalcitonin, the uncut precursor that contains katacalcin, is a blood test for serious bacterial infection. That test measures procalcitonin, a different molecule, and its studies are not carded here. In septicaemia the precursor circulates largely uncut, and in one comparison free katacalcin was undetectable in septic serum though present in medullary thyroid cancer.
Katacalcin has never been a medicine. No study read gave it to a person, no product exists, and neither Drugs@FDA nor the EMA medicines list holds a record for it. It is a laboratory analyte, a fragment of a hormone precursor, and almost all of the human work on it dates from 1983 to 1995.
Mechanism of Action
Katacalcin is the C-terminal end of preprocalcitonin, split off with calcitonin in thyroid C cells and released with it when blood calcium rises; a hormone action in people has not been shown.
Cut from the calcitonin precursor
Processing of preprocalcitonin frees calcitonin and katacalcin from the same chain, so the two are stored in the same C cells.
Released with calcitonin
Calcium raises both within minutes in healthy people, in near-equal molar amounts, which is why katacalcin was studied as a second tumour marker.
A cell effect in the lab
In a dish it drew human monocytes toward it through cyclic AMP and protein kinase A; no matching effect has been shown in a person.
Published Research
These are studies of katacalcin itself, read from their PubMed abstracts: the discovery paper, assays in healthy people and in patients with thyroid and lung cancer, measurements in tissue, milk and semen, one cell study and one mouse study. No study read gave katacalcin to a person. Studies of calcitonin and of procalcitonin are carded on their own molecules, not here.
Named, measured and proposed as a hormone
The paper that named katacalcin reported it in the plasma of all 57 healthy volunteers tested, at levels higher in men than in women and roughly matching calcitonin mole for mole. Its level doubled within five minutes of a calcium infusion and was greatly raised in 20 people with medullary thyroid carcinoma. The authors described it as a calcium-lowering hormone and suggested it might help in bone disease; the abstract does not say how the calcium effect was shown.
Found in the same thyroid cells as calcitonin
Antibodies raised against synthetic katacalcin and against calcitonin were used on tissue from 8 medullary thyroid carcinomas and 6 normal thyroids, three adult and three fetal. In every sample both peptides sat in the same C cells, normal or cancerous, under the light and the electron microscope. The study showed that a peptide predicted only from a gene sequence could be found in real tissue.
Levels compared in Gambian and British adults
Blood calcitonin and katacalcin were measured in black Gambian and white British adults to look for a reason why osteoporosis is more common in some groups. Men had higher levels of both peptides than women. The finding the authors stressed concerned calcitonin: white women had the lowest calcitonin of any group.
A serum test that complements calcitonin
A radioimmunoassay for PDN-21 in unprocessed serum detected it in 92% of healthy people, while calcitonin was measurable in only 25% before stimulation. A one-minute calcium injection raised PDN-21 4.8-fold in men and 2.0-fold in women; pentagastrin did not raise it in healthy people. Levels were normal in chronic high calcium from overactive parathyroids, raised and stimulable in 41 patients with medullary thyroid carcinoma, and rose after pentagastrin in 5 patients' siblings suspected of early C-cell disease.
Removing the ovaries left levels unchanged
Seventeen women aged 26 to 51 had a calcium infusion test before and 14 days after hysterectomy with removal of both ovaries. Basal and peak katacalcin did not change significantly (basal about 3.2 versus 3.9 ng/L), and neither did calcitonin, although the shape of the response curves differed after surgery, which the authors read as a change in how the peptides are handled.
A more sensitive assay in healthy adults
Extracting serum on C18 cartridges before radioimmunoassay brought the detection limit for katacalcin down to 0.8 pmol/L and made the test specific for the free peptide. Mean basal katacalcin was 3.0 pmol/L in men under 40, 1.8 in older men, 2.1 in younger women and 1.3 in older women, the last group being significantly lower. Katacalcin and calcitonin levels rose and fell together across the subjects.
In seminal fluid, mostly as larger forms
A direct assay found calcitonin-type immunoreactivity in seminal plasma from 74 men at several times the usual serum level, with no relation to sperm measures. In a pooled sample from 25 men, the free forms of calcitonin and katacalcin were present only at about plasma levels, so the high readings came from two larger peptides. The authors found no effect on fertility.
A tumour marker as useful as calcitonin
In 22 patients with C-cell (medullary) thyroid cancer, basal serum katacalcin ranged from 0.32 to 290 ng/mL against a normal range below about 0.15 ng/mL, and it tracked calcitonin closely (r = 0.98). Both rose after pentagastrin or calcium and were released in near-equal molar amounts. Blood drawn from veins near the tumour carried higher levels, which surgery confirmed, and levels followed disease stage over time.
Human milk carries the precursor
Seventeen samples of human milk held katacalcin-type immunoreactivity at about the same molar level as calcitonin-type immunoreactivity, around 190 and 210 pmol/L. Most of it ran as large molecules on gel filtration, and digesting them with trypsin released a fragment the size of synthetic katacalcin, evidence that milk contains uncut calcitonin precursor.
Released together with calcitonin in healthy people
In nine healthy men and nine healthy women, a cartridge-extraction assay detected katacalcin in every plasma sample. Basal levels were higher in men (4.7 against 3.3 ng/L), and a five-minute calcium infusion raised them sharply, by about 30 ng/L in men and 11 ng/L in women. Molar levels of katacalcin and calcitonin correlated closely (r = 0.97), showing that normal C cells release both under the control of blood calcium.
Its forms inside a thyroid tumour
Peptides were purified from a human medullary thyroid carcinoma and identified by amino-acid sequencing and mass spectrometry. Full-length katacalcin (residues 1-21) was the main form, but shorter pieces trimmed from its end, 1-20, 1-19, 1-15 and 1-13, were also present at high levels, showing that the tumour breaks katacalcin down as well as making it.
Also made in the prostate
Immunostaining and electron microscopy of human prostate and urethra found calcitonin in a group of scattered endocrine-type cells, and the same cells also held katacalcin and CGRP. Calcitonin sat in secretory granules. The authors concluded that the calcitonin gene is active in these cells, which may release its products into ducts and nearby tissue.
More often raised than calcitonin in lung cancer
In 249 people with advanced lung cancer, PDN-21 was above the healthy 95th percentile in 44%, against 19% for calcitonin, and in small-cell lung cancer 51% against 23%. It was raised in about a third of patients whose calcitonin was normal, but in only 9% of people with benign lung disease. It added information to the established markers NSE and CEA.
First values in children
Serum PDN-21 averaged 12.3 pg/mL in 16 healthy children aged 3 to 11, with no difference between boys and girls, and 14.0 pg/mL in 21 children with spasmophilia, a difference that was not significant. PDN-21 and calcitonin rose and fell together in both groups. The authors noted that what PDN-21 does in the body was still unknown.
Very high in medullary thyroid carcinoma
All 10 patients with medullary thyroid carcinoma had extremely high plasma PDN-21. Their PDN-21 levels correlated significantly with calcitonin and with CGRP, the other products of the same gene, and the authors proposed it as a marker for finding the cancer.
Equivalent to calcitonin for diagnosis
PDN-21 was detectable in 73% of 40 healthy people, and pentagastrin made it detectable in 7 of 17 who started below the limit. In 65 patients with medullary thyroid carcinoma it matched calcitonin almost exactly (r = 0.99, molar ratio near 1). In one patient's venous sampling the rise near the tumour was larger for PDN-21 than for calcitonin, and the authors advised measuring it whenever calcitonin results are borderline.
Compared with chromogranin A
In the same 65 patients with medullary thyroid carcinoma, PDN-21 rose and fell with calcitonin, rose with it after pentagastrin, and helped locate tumours by venous sampling. Chromogranin A, another tumour marker, was raised mainly in advanced disease, did not respond to pentagastrin and was of little use for early diagnosis or locating tumours. The authors judged PDN-21 an independent second test for diagnosis and follow-up.
Less responsive than calcitonin in family screening
In relatives screened for the inherited MEN-2 syndrome, some with C-cell hyperplasia or early cancer, both peptides could pick out affected people. But calcitonin's resting level rose more with C-cell overactivity, and its rise after pentagastrin was larger than PDN-21's (both P < 0.01). The authors put the gap down to differences in how the two peptides are released and cleared.
Normal in Turner syndrome with osteoporosis
Fifteen girls with Turner syndrome and osteoporosis and 15 matched healthy girls had basal and calcium-stimulated measurements of calcitonin and katacalcin. Neither basal nor stimulated katacalcin differed between the groups, even after correcting for each girl's rise in ionised calcium, so the authors ruled out a C-cell hormone shortfall as the cause of bone loss in this syndrome.
A sharp rise with residual or returning cancer
A new radioimmunoassay set the upper normal limit of serum PDN-21 at 67 pg/mL in 98 healthy people. Among patients with a range of thyroid diseases, only those with medullary carcinoma had raised levels: 110 to 18,300 pg/mL in 7 patients before surgery, and 64 to 140,000 pg/mL in 18 after it, with the highest values where tumour remained or came back.
Raised in women with lupus on steroids
In 52 premenopausal women with systemic lupus erythematosus taking glucocorticoids, mean PDN-21 was 354.6 pg/mL against 66.7 pg/mL in healthy women, while calcitonin did not differ. The authors suggested, without testing it, that the steroids raise gastrin through effects on the stomach and so stimulate the C cells.
Free katacalcin is missing in septicaemia
Serum from patients with septicaemia and from patients with medullary thyroid carcinoma was separated by chromatography and probed with antibodies to each part of procalcitonin. Free PDN-21 was found in the cancer patients' serum but was undetectable in septic serum, where uncut procalcitonin and larger fragments still carrying the PDN-21 sequence circulated instead. The precursor is processed differently in infection.
It draws human monocytes in a dish
Monocytes (CD14+ cells) and neutrophils were taken from healthy donors and tested in a chemotaxis chamber. Katacalcin made the monocytes migrate toward it over an extremely wide concentration range, from attomolar to micromolar, and blunted their response to other attractants; neutrophils did not respond. The effect ran through cyclic AMP and protein kinase A and needed pertussis toxin-sensitive G proteins. The N-terminal flanking peptide of procalcitonin had no such effect.
No effect alone on mouse thyroid output
In mice prepared to read thyroid hormone release from blood radioiodine, calcitonin lowered resting levels, apparently through the kidney, but katacalcin and CGRP did not. None of the three peptides alone changed the response to TSH. Given together in pairs or all three at once, they damped the TSH-driven rise, which the authors proposed as a local control inside the thyroid.
No Established Human Dose
No study read has given katacalcin to a person. Every human study on this page measures it: in blood the body has released, in tissue sections, in milk and in seminal fluid. The stimulation tests that raise it give calcium or pentagastrin, not katacalcin. The only studies that applied the peptide itself used human white cells in a dish and mice, so there is no katacalcin preparation for people and no human dose to state.
What this rests on: PMID 3902867, PMID 3350911, PMID 12369791, PMID 2784248.
Educational information, not medical advice. The doses on this page come from approved labels, published studies and, where no study exists, amounts reported by users. None is a recommendation for you. An unapproved compound has no established safe or effective human dose, and products sold for “research use only” are not made or tested for people. Talk to a doctor before acting on anything on this site, including before you start, stop or change any medicine or dose. Full medical disclaimer.
What a Buyer Needs to Know
What is sold, how it is mixed, stored and taken, and what is known about its safety, quality and legal status. Each part names its source. Where we have none, it says unknown.
What is sold
Unknown: we hold no label and no published test that says what forms or vial sizes Katacalcin is sold in. A vial's own label is a seller's claim, not a source.
Mixing a vial: a worked example
Unknown: no human dose of Katacalcin has been established (see No Established Human Dose below), so there is no amount to work out. The reconstitution calculator does the arithmetic for any vial, water and dose.
Storage before and after mixing
Unknown: no label or published stability study on file says how to store Katacalcin, before or after mixing. The mixing guide sets out the general rules, with their sources: keep a mixed vial in the fridge, and use it promptly, as the bacteriostatic water label says of any drug dissolved in it. The 28 days often quoted is the limit for an opened multiple-dose vial from a manufacturer, an outer limit set for sterility, not a time a mixed solution has been shown to keep. Nobody has published how long Katacalcin stays intact once mixed.
How it is taken
Unknown: with no established human dose, there is no established way of taking Katacalcin. What the human studies gave and how is set out under No Established Human Dose.
What to expect, and when
Unknown: no cited half-life and no label or trial duration on this page says how long Katacalcin lasts or how long it was given. Results reported in the studies are under Published Research.
Side effects, and when to stop or get help
From the Side Effects section: Every human study read measured the peptide the body releases; none gave it (PMID 3902867); The only applied-peptide work used human monocytes in a dish and mice (PMIDs 12369791, 2784248). Full list and cautions ↓
When to stop or get help: unknown; no label or trial on file sets rules for stopping Katacalcin. Treat a severe or unexpected reaction as a reason to stop and see a doctor.
Source: the Side Effects section below (“Katacalcin has not been given to people, so no human side effects are known”).
Interactions
Unknown: a PubMed search for human interaction studies of Katacalcin (reviewed 2026-11-03) found none. Unknown is not the same as safe to combine.
Every peptide's record, with its source: the interaction matrix.
Checking what you bought
Unknown: no published independent test of Katacalcin products is in our lab-results database yet, so how products sold under this name measure up is not known.
To read a certificate of analysis, paste it into the COA decoder; it checks the measured mass against Katacalcin's expected mass, 2,436.6 Da, from this entry's molecular data. Trust & Verification explains what independent testing can and cannot show.
Legal status
US: Research Chemical (Not a medicine: katacalcin has only been measured in people, by radioimmunoassay (PMID 3902867), never given). Sport: Not on the 2026 List.
Country by country ↓ · Regulatory tracker
Source: this entry's approval status and the WADA Prohibited List, as in Legal Status below.
Side Effects & Contraindications
Reported Side Effects
Katacalcin has not been given to people, so no human side effects are known.
Contraindications & Cautions
No product label exists. These cautions follow from the evidence.
Legal Status
Katacalcin is a laboratory analyte and research peptide; it is not approved as a medicine anywhere in the sources read.
Frequently Asked Questions
?What is katacalcin?
A 21-amino-acid peptide cut from the far end of the calcitonin precursor in thyroid C cells. It is released with calcitonin and is also called PDN-21.
?Does katacalcin lower calcium?
Its discoverers proposed that it did, but no study read showed that effect in people, and later papers called its role unknown.
?Is katacalcin the same as procalcitonin?
No. Procalcitonin is the whole uncut precursor that contains both calcitonin and katacalcin; it is measured in serious bacterial infection. Katacalcin is one piece of it.
?What was katacalcin measured for?
Mainly as a tumour marker for medullary thyroid carcinoma, where it rises with calcitonin. It was also tested in lung cancer and in studies of bone and calcium.
?Is it a better marker than calcitonin?
Studies disagreed. Some found it equivalent or slightly more sensitive in borderline cases; a family-screening study found calcitonin responded more strongly in early disease.
?Can you take katacalcin?
No. It has never been given to a person in any study read, and no medicine or approved product contains it.
References
- [pubmed] Hillyard CJ, et al. "Katacalcin: a new plasma calcium-lowering hormone." Lancet, 1983;1(8329):846-8. PMID: 6132180.
- [pubmed] Ali-Rachedi A, et al. "Immunocytochemical localisation of katacalcin, a calcium-lowering hormone cleaved from the human calcitonin precursor." J Clin Endocrinol Metab, 1983;57(3):680-2. PMID: 6348069.
- [pubmed] Stevenson JC, et al. "Racial differences in calcitonin and katacalcin." Calcif Tissue Int, 1984;36(6):725-8. PMID: 6442208.
- [pubmed] Ittner J, et al. "Diagnostic evaluation of measurements of carboxyl-terminal flanking peptide (PDN-21) of the human calcitonin gene in human serum." J Clin Endocrinol Metab, 1985;61(6):1133-7. PMID: 3902867.
- [pubmed] Marton IS, et al. "Effect of calcium loading test on calcitonin and katacalcin levels before and after surgical removal of the ovaries." Exp Clin Endocrinol, 1985;86(3):361-4. PMID: 3841516.
- [pubmed] Woloszczuk W, et al. "Determination of circulating monomeric katacalcin and calcitonin: physiological studies in normal subjects." J Clin Chem Clin Biochem, 1986;24(7):451-5. PMID: 3755463.
- [pubmed] Maier U, et al. "Calcitonin- and katacalcin-like immunoreactivity in human seminal plasma." Exp Clin Endocrinol, 1986;88(1):89-94. PMID: 3817006.
- [pubmed] Raue F, et al. "[Katacalcin--a new tumor marker in C-cell cancer of the thyroid gland]." Klin Wochenschr, 1987;65(2):82-6. PMID: 3550267.
- [pubmed] Bucht E, et al. "Evidence for precursors of calcitonin/PDN 21 in human milk." Regul Pept, 1987;19(1-2):65-71. PMID: 3685455.
- [pubmed] Hurley DL, et al. "Cosecretion of calcitonin gene products: studies with a C18 cartridge extraction method for human plasma PDN-21 (katacalcin)." J Clin Endocrinol Metab, 1988;66(3):640-4. PMID: 3350911.
- [pubmed] Conlon JM, et al. "Molecular forms of katacalcin, calcitonin gene-related peptide and gastrin-releasing peptide, in a human medullary thyroid carcinoma." Cancer Res, 1988;48(9):2412-6. PMID: 3258543.
- [pubmed] di Sant'Agnese PA, et al. "Calcitonin, katacalcin, and calcitonin gene-related peptide in the human prostate. An immunocytochemical and immunoelectron microscopic study." Arch Pathol Lab Med, 1989;113(7):790-6. PMID: 2787149.
- [pubmed] Body JJ, et al. "A preliminary evaluation of calcitonin and PDN-21 as tumor markers for lung cancer. EORTC Lung Cancer Working Party." Henry Ford Hosp Med J, 1989;37(3-4):190-3. PMID: 2639133.
- [pubmed] Saggese G, et al. "[Katacalcin levels in healthy children and children with spasmophilia]." Minerva Pediatr, 1989;41(9):459-66. PMID: 2685535.
- [pubmed] Takami H, et al. "PDN-21: possible tumor marker for medullary thyroid carcinoma." J Surg Oncol, 1990;44(4):205-7. PMID: 2385096.
- [pubmed] Blind E, et al. "Evaluation of sensitive PDN-21 (katacalcin) determination as tumor marker in medullary thyroid carcinoma." J Endocrinol Invest, 1992;15(2):93-8. PMID: 1569295.
- [pubmed] Raue F, et al. "PDN-21 (katacalcin) and chromogranin A: tumor markers for medullary thyroid carcinoma." Henry Ford Hosp Med J, 1992;40(3-4):296-8. PMID: 1483876.
- [pubmed] Schifter S. "Calcitonin and PDN-21 as tumour markers in MEN-2 family screening for medullary thyroid carcinoma." Eur J Cancer, 1992;28(2-3):341-5. PMID: 1350454.
- [pubmed] Saggese G, et al. "Assessment of thyroidal "C" cell secretion in osteoporotic girls with Turner's syndrome. Basal and calcium-stimulated levels of total calcitonin, extractable calcitonin and katakalcin." Acta Paediatr, 1992;81(6-7):532-5. PMID: 1392368.
- [pubmed] Takami H. "Measurement of serum PDN-21 (Katacalcin) levels by radioimmunoassay in patients with various thyroid diseases." Exp Clin Endocrinol, 1994;102(5):370-3. PMID: 7867699.
- [pubmed] Navarro MA, et al. "PDN-21 in premenopausal women with systemic lupus erythematosus treated with glucocorticoids." J Rheumatol, 1995;22(12):2238-40. PMID: 8835555.
- [pubmed] Ittner L, et al. "Circulating procalcitonin and cleavage products in septicaemia compared with medullary thyroid carcinoma." Eur J Endocrinol, 2002;147(6):727-31. PMID: 12457446.
- [pubmed] Kaneider NC, et al. "Involvement of cyclic adenosine monophosphate-dependent protein kinase A and pertussis toxin-sensitive G proteins in the migratory response of human CD14+ mononuclear cells to katacalcin." J Bone Miner Res, 2002;17(10):1872-82. PMID: 12369791.
- [pubmed] Ahrén B. "Effects of calcitonin, katacalcin, and calcitonin gene-related peptide on basal and TSH-stimulated thyroid hormone secretion in the mouse." Acta Physiol Scand, 1989;135(2):133-7. PMID: 2784248.
- [other] UniProt P01258 (CALC_HUMAN), calcitonin precursor; peptide 121-141 is katacalcin (DMSSDLERDHRPHVSMPQNAN), free C-terminus. Read November 3, 2026. https://www.uniprot.org/uniprotkb/P01258/entry
Sources & Citations
Every study on this page was read from its PubMed record on November 3, 2026. The sequence and precursor positions come from UniProt P01258; regulatory status comes from Drugs@FDA (openFDA) and the EMA medicines list, read the same day. Grey Peptides sells nothing and links to no vendor.
Medical Disclaimer: This content is for educational and informational purposes only. It is not medical advice, and nothing here is an instruction to obtain or use any compound. Talk to a licensed clinician about your own situation.