.png)
Skrevet av Nora.Heime.net
Om historien til Thyroxin og Thyroid, Erfa Thyroid (før: Pfizer Canada) tørket kjertel, Thyreoidum, Thyreodinum etc.
Standarden er Thyroid, tørket kjertel av svin. All forskning på Thyroxin ble i virkeligheten gjort på Thyroid, for i gamle dager fantes det ikke T4 men det ble forsket flittig på Thyroid som også ble kalt Thyroxine fordi man ikke visste bedre.
Dette heter Thyroid USP (United States Pharmacopeia) hvor innholdet av Thyroxin og Liothyronin nå er strengt regulert. I gamle dager kjente man ikke til T4 og T3 så det ble regulert etter jodinnhold. Det tillates 10 % avvik i styrken. (90%-110%) Dette gjelder alle Thyroxinpreparater, og alle medisiner forøvrig. For generics gjelder 80-125%.
Det fins ingen generic for Thyroid, derfor gjelder de 10 prosentene. (Oppdatert: det er blitt forandret nå, til 95-105%)
Thyroid ble tidlig standardisert og produsert som merkevarer. Et eksempel som ligger på internett er Merck thyroidinum.
I begynnelsen var kravet at det skulle analyseres etter jodinnhold, senere da det var mulig målte man selvsagt mengden Levothyroxin og Liothyronin.
Her er en interessant Cubansk nettside hvor de lister opp alle de gamle navn og produsenter på Thyroid: http://www.sld.cu/servicios/medicamentos/medicamentos_list.php?id=399
Liste over gamle og nye preparater:
Preparatnavn | Land | Produsent |
Thyranon | Sverige | |
Thyreoïdum | Danmark, Nederland | Biofac Kastrup, importert til Nederland av BUFA/Fargo |
Thyroidin | Tyskland | |
Armour Thyroid | USA | Flere over tiden: USV, Pfizer, Forest, nå kjøpt opp av Activas Pharmaceuticals |
NP Thyroid | USA | Acella Pharmaceuticals |
Nature-Throid, Westhroid Pure | USA | Western Reseach Laboratories http://www.rlclabs.com disse skaffet på 2000-tallet en sentral godkjenning av Nature-throid i UK og gikk gjennom alle disse godkjenningsprosedyrene |
ERFA Thyroid | Canada | Parke-Davis, kjøpt opp av Erfa (hovedkontor: Belgia) |
Thyroid Powder, USP | Canada | Medisca (kun tilgjengelig via compounding pharmacies) |
Cinetic | Italia | Teofarma SRL |
Thyreoid | Tyskland | |
Tiroides | Spania | |
? | Japan | |
Thyroidine | Frankike | |
Thyroid-S | Thailand | Sriprasit |
Thiroyd | Thailand | Greater Pharma |
Thyroid API | Spania | Bioiberica |
Adthza | USA | Azurity Pharmaceuticals |
Thyrid Extract | Australia | Australian Custom Pharmaceuticals |
Compound Thyroid | Danmark | Glostrup Apotek |
Thyreogland | Tyskland | Klösterl-Apotheke, Munchen |
Schilddruesen-Extrakt | Tyskland | Receptura |
Whole Thyroid | New Zealand | Pharmaceutical Compounding New Zealand |
Diotroxin | Sør-Afrika | Aspen Pharmacare Ltd |
Generic Thyroid | USA | Major Pharmaceuticals |
Qualitest | USA | Time-Caps Labs |
Thyrolar | USA | Forest Labs |
Thyrogold | USA | Natural Thyroid Solution (ikke reseptbelagt, men anbefalt av Dr. Lowe) |
Noen av disse finnes ikke lenger på markedet.
Thyroid USP har innhold av T4 og T3 som er strengt regulert, det er det USP betyr, United States Pharmacopeia. Spesifikajsonen er at 1 grain inneholder 38 mcg T4 pluss 9 mcg T3, pluss minus 10%. Dette er helt pålitelig. 1 grain = 60 mg.
I Europa har Thyreoïdum og andre lignende produkter ikke dette kravet, men alle batches med thyreoidum fra Danmark blir analysert og mengden T4 og T3 er spesifikt angitt. Det er altså ikke engang 10% slingringsmonn engang. Det er høyere andel av T3 i Thyreoidum. Det er vel dette som Wiersinga kommer inn på.
Men hans uttalelse blir brukt om upålitelighet av Armour Thyroid av Welsh i Australia og William Harper i Canada her.
Wiersinga holder til i Holland, Welsh i Australia, og Harper i Canada.
I Australia fins ikke Armour, de bruker pulver fra USA og apotekene lager kapsler.
I Holland bruker man Thyreoïdum, og i Canada fins ikke Armour, de lager eget, men av importert råstoff.
(Det var Pfizer som eide Armour Thyroid den gangen, og så splittet Pfizer seg opp i Canada og USA og slik fikk Canada den originale gamle Armour-formuleringen før alle reformuleringene. Armour fikk ingen rettigheter for markedsføring til utlandet, det var det Thyroid i Canada som fikk.
Så kjøpte Erfa opp et knippe rettigheter, og satset på Thyroid etter pasientønsker. Det er godkjent av Health Canada, noe som er viktig for oss i Europa siden det ofte er en forutsetning at medisinen må være godkjent i opprinnelseslandet for at det overhodet kan godkjennes i Europa)
Her i Europa hadde vi Merck Thyroidin i følge deres egen nettside, men jeg har ikke oversikt over alle merkene som fantes, jeg har funnet et merke fra Sveits også. Fremdeles lages det thyreoidum i Danmark, det er det som de Hollandske pasientene bruker idag.
Armour Thyroid fra Forest har ikke rettigheter utenfor USA, ikke engang Canada. Det kom av at Pfizer, som eide rettighetene, ble delt opp i USA og Canada og de delte opp rettighetene til Armour og Thyroid. Thyroid fra Canada er den opprinnelige Armour pga de gamle rettighetene.
Western Research Laboratories har fått godkjent (sentral godkjenning, men alle må søke registreringsfritak, som heter named-patient program på utenlandsk) sitt merke Nature-Throid her i Europa, de gikk gjennom godkjenningsprosedyren i England og det gjelder dermed i hele Europa. Det er like så pålitelig. Alt kommer jo av samme råstoff. http://thyroid.about.com/cs/thyroiddrugs/a/naturethroid.htm
Det som skiller det amerikanske USP (United States Pharmacopeia) Thyroid fra det europeiske, er at forhodet mellom T4 og T3 er konstant og at styrken er lik hele tiden, noe som er en fordel når man lager piller av det. (Kommentar fra en farmaseut på Stenlake Pharmacy i Australia).
Det europeiske Thyreoidum har varierende styrke og forhold mellom T4 og T4 for hver batch, som varer ett år omtrent. På direkte forespørsel til brukerne, sier de at det ikke har noen konsekvenser (forumet i Holland). I tillegg har man Thyroid fremdeles i Japan og i Thailand.
Oppdatert: I følge eget forum sier Erfa at de skaffet Thyroid-råstoff i europa. Det kan godt være fra biofac i Danmark, og det eksporteres jo noen titalls millioner svinekjertler fra Danmark ifølge dansker på Sonjas Stoffskifteforum. De kan altså antageligvis lage Thyroid med USP-spesifikasjoner også.
Ihvertfall er virkningen helt utmerket i følge alle pasienter som har prøvd det. Mengden virkestoff er også oppgitt som mindre enn Armour hadde, men virkningen er den samme som gammelt Armour fra da den var god. Andre pasienter har også bemerket at for Levothyroxin så var virkningen av europeiske tabletter sterkere enn for amerikanske.
Nå trodde man at thyroxin (=t4) var det aktive stoffet i Thyroid, og det kom levothyroxin (=t4) på markedet. Det ble hevdet at det var akkurat det samme som Thyroid. Det ble aldri gjennomført doble blindtester for å bevise at Levothyroxin virket like bra på pasientene som Thyroid av den grunn (Merk at det er gjort minst 14 sammenligningsstudier).
Det er grunnen til at vi idag ikke kan vise til doble blindtester for at Armour Thyroid er like effektivt som Thyroxin, eller at pasienter i slike tester følte seg bedre eller dårligere. Det kommer av produsentene til Thyroxin som hele tiden hevdet det var det samme som Thyroid.
Oppdatering: Dr. Lowe har funnet minst 14 direkte sammenligninger av Thyroid vs Thyroxin i litteraturen. Han sier det er feil, en gjentatt løgn, at det ikke fins sammenlignende studier mellom de to. Thyroid var anerkjent som stabilt og effektivt.
Så kom en opprydding av medisiner i USA. Alle som hadde vært brukt i mange år og vist seg effektive, fikk status som godkjent på historisk grunn. Merk at det ved søknad om godkjenning i Norge kan gis et unntak på å fremlegge dokumentasjon i kliniske forsøk, nemlig historisk bruk. Digitalis og Thyroid er nettopp slike midler.
Synthroid, som thyroxin het i USA, påberopte seg historisk status og henviste til Thyroid, at det var det samme som Thyroid. De greide å vri seg unna helt til FDA skjærte gjennom og bestemte at alle Levothyroxin-produkter er nye medisiner og at de måtte gjennomgå nye godkjenningsprosedyrer og bevise sin stabilitet ved oppbevaring og dosestabilitet.
Synthroid var beryktet for at de gjentakende ganger forandret på ingrediensene og aktive stoffer og at styrken kunne være mye mer eller mindre enn oppgitt. Mange pasienter var veldig misfornøyde fordi de ble så dårlige at de fungerte dårlig i jobben etc.
En større skandale var også saken hvor Knoll som eide Synthroid da forhindret en forskningsrapport som skulle trykkes, om at Synthroid ikke var bedre enn andre merker. Det var en så stor skandale når det kom ut, at de sparket forskeren og hindret utgivelsen av korrekt utført forskning.
Og så var det en større erstatningssak i kjølvann av dette, hvor pasientene fikk tilbake noen dollar for overprisen de måtte betale mens i virkeligheten alle Levothyroxinpreparater var likeverdige. Pasientene hadde betalt en stor overpris fordi Synthroid hadde hevdet at de var de andre langt overlegen. Synthroid koster ca 52 dollar for 90 tabletter mot Thyroxine i England ca 2,50 pund og Levaxin her ca 70 kr for 100 stk.
Synthroid er kjent for å være inkonsistent, ikke Thyroid. Om man søker i databasen for tilbakekallinger i USA, er det Levothyroxin som er tilbakekalt, ikke Thyroid.
De forskjellige merker Levothyroxin, til tross for at de skal inneholde det samme, skal ikke brukes om hverandre fordi de vil gi forskjellige blodverdier. Hvis man bytter, må man ta nye blodprøver etter 6 uker.
De forskjellige produsenter av Levothyroxin kjempet i mange år mot å måtte søke om godkjenning. De hevdet hele tiden at deres produkt var identisk med Thyroid, som jo var anerkjent som stabil og med god effekt.
NDA = New Drug Application. Godkjenning på historisk grunnlag heter "Grandfathered In".
1891: Murray behandler pasienter med Thyroid ekstrakt med injeksjoner. Like etter tar man i bruk perorale midler og tabletter lages.
1915: Kendall lager et krystallinsk pulver fra Thyroid. Man antar at Thyroxin er det aktive stoffet i Thyroid.
1950-tallet: T3, liothyronin ble isolert og laget kjemisk. Man var ikke klar over at det var mer i Thyroid USP enn T4 før det.
1950: Thyroxin-Natrium registrert i Norge.
1952: T3 ble oppdaget, viktig info fordi man jo innførte Thyroxin-Natrium som identisk med Thyroidekstrakt før man ante noe om det aktive virkestoffet T3, og at det manglet i Thyroxin-Natrium. Men fra før visste man at T2 var 80% av mengden Thyroxintyper i Thyroidekstrakt, men det virket ikke i forsøk så man avskrev dette som ikke viktig.
1958: Synthroid kommer inn i handelen i USA.
1962: Medisiner som var anerkjente som effektive før det, trengte ikke søke om ny godkjenning senere. Dette er et prinsipp som er kjent som "Grandfathered In".
1997: FDA bestemmer at alle Thyroxin-preparater er nye legemidler og må levere en søknad for godkjenning av ny medisin. Ikke lenge etter blir Thyrolar, et T4/t3 kombinasjonspreparat (Liotrix) godkjent som første preparat.
2000: Unithyroid er godkjent som første Levothyroxinpreparat i USA. Merk at Thyrolar (en T4/T3-kombo eid av Forest) søkte og fikk godkjennelse lenge før noen Levothyroxinpreparater. Armour Thyroid og all Thyroid USP var hele tiden godkjent.
2001: Abbott som nå eier Synthroid leverer NDA søknad.
Juli 2002: Synthroid godkjent.
Referanser:
Har fulgt tett med på spørsmålene om stoffskiftemedisiner.
Bemerk at Federal Register er det mest offisielle som kan gjøres i USA, det er der nye lover blir registrert. Et ganske viktig dokument om ustabiliteten av Levothyroxin. Ingen kan komme her og komme her og si at det er løgn at Levothyroxin er ustabil. Det er Levothyroxin og ikke Thyroid USP som er upålitelig og ustabil.
http://www.pharmabiz.com/article/detnews.asp?Arch=&articleid=6645§ionid=14 Abbott leverer NDA søknad.
Om historien, Thyroid extract etc.
En kort oversikt over medisiner i USA inkludert Thyrolar.
Mer om skandalen og rettssaken om Synthroid og Boots/Knoll. "In April of 1997, the Journal of the American Medical Association (JAMA) published a study, commissioned by Knoll, that concluded that Synthroid -- a synthetic thyroid hormone -- is no better than two generic alternatives or the brand-name drug Levoxyl. Knoll disagreed with the study, and considered suing to stop its publication. Betty Dong, the researcher at the University of California at San Francisco who conducted the study, told the journal that Knoll had suppressed her findings for more than six years."
Unithyroid godkjent som første L-Thyroxinpreparat 2000.
2001 "Levothyroxine sodium tablets are also currently not listed in the Orange Book. In the words of the FDA, "Levothyroxine sodium was first introduced into the market before 1962 without an approved NDA, apparently in the belief that it was not a new drug."
Se også lenger ned en forklaring til bioekvivalens.
2001 Synthroid ennå ikke godkjent: FDA is penalizing companies that filed late for approval of Levothyroxine Sodium products by forcing reductions in distribution over the next 2 years.
Synthroid godkjent 2002
Blant annet:
IV. Formulation Change
Because orally administered levothyroxine sodium products are marketed without approved applications, manufacturers have not sought FDA approval each time they reformulate their products. In 1982, for example, one manufacturer reformulated its levothyroxine sodium product by removing two inactive ingredients and changing the physical form of coloring agents (Ref. 6).
The reformulated product increased significantly in potency. One study found that the reformulated product contained 100 percent of stated content compared to 78 percent before the reformulation (Ref. 7).
Another study estimated that the levothyroxine content of the old formulation was approximately 70 percent of the stated value (Ref. 8).
This increase in product potency resulted in serious clinical problems. On January 17, 1984, a physician reported to FDA: ''I have noticed a recent significant problem with the use of [this levothyroxine sodium product]. People who have been on it for years are suddenly becoming toxic on the same dose. Also, people starting on the medication become toxic on 0.1 mg [milligram] which is unheard of.''
On May 25, 1984, another physician reported that 15 to 20 percent of his patients using the product had become hyperthyroid although they had been completely controlled up until that time. Another doctor reported in May 1984 that three patients, previously well-controlled on the product, had developed thyroid toxicity. One of these patients experienced atrial fibrillation.
There is evidence that manufacturers continue to make formulation changes to orally administered levothyroxine sodium products. As discussed in section V of this document, one manufacturer is reformulating in order to make its product stable at room temperature.
In a 1990 study (Ref. 5), one manufacturer's levothyroxine sodium tablets selected from different batches showed variations in chromatographs suggesting that different excipients had been used.
V. Stability Problems
FDA, in conjunction with the United States Pharmacopeial Convention, took the initiative in organizing a workshop in 1982 to set the standard for the use of a stability-indicating high-performance liquid chromatographic (HPLC) assay for the quality control of thyroid hormone drug products (Ref. 3).
The former assay method was based on iodine content and was not stability-indicating. Using the HPLC method, there have been numerous reports indicating problems with the stability of orally administered levothyroxine sodium products in the past several years. Almost every manufacturer of orally administered levothyroxine sodium products, including the market leader, has reported recalls that were the result of potency or stability problems.
Since 1991, there have been no less than 10 firm-initiated recalls of levothyroxine sodium tablets involving 150 lots and more than 100 million tablets. In all but one case, the recalls were initiated because tablets were found to be subpotent or potency could not be assured through the expiration date.
The remaining recall was initiated for a product that was found to be superpotent. During this period, FDA also issued two warning letters to manufacturers citing stability problems with orally administered levothyroxine sodium products.
At one firm, potency problems with levothyroxine sodium tablets resulted in destruction of products and repeated recalls. From 1990 to 1992, the firm destroyed 46 lots of levothyroxine sodium tablets that failed to meet potency or content uniformity specifications during finished product testing. In August 1989, this firm recalled 21 lots due to subpotency. In 1991, the firm recalled 26 lots in February and 15 lots in June because of subpotency.
An FDA inspection report concerning another manufacturer of levothyroxine sodium showed that 14 percent of all lots manufactured from 1991 through 1993 were rejected and destroyed for failure to meet the assay specifications of 103 to 110 percent established by the firm.
In March 1993, FDA sent a warning letter to a firm stating that its levothyroxine tablets were adulterated because the expiration date was not supported by adequate stability studies. Five lots of the firm's levothyroxine sodium tablets, labeled for storage within controlled room temperature range, had recently failed stability testing when stored at the higher end of the range.
The warning letter also objected to the labeled storage conditions specifying a nonstandard storage range of 15 to 22 degrees C. FDA objected to this labeling because it did not conform to any storage conditions defined in United States Pharmacopeia (USP) XXII. In response, the firm changed the labeling instruction to store the product at 8 to 15 degrees C. The firm informed FDA that it would reformulate its levothyroxine sodium tablets to be stable at room temperature.
The five failing lots named in FDA's warning letter were recalled in April 1994. Previously, in December 1993, a lot of levothyroxine sodium tablets was recalled by the same firm because potency was not assured through the expiration date. In November 1994, the renamed successor firm recalled one lot of levothyroxine sodium tablets due to superpotency.
Another firm recalled six lots of levothyroxine sodium tablets in 1993 because they fell below potency, or would have fallen below potency, before the expiration date. The USP specifies a potency range for levothyroxine sodium from 90 percent to 110 percent. Analysis of the recalled tablets showed potencies ranging from 74.7 percent to 90.4 percent. Six months later, this firm recalled another lot of levothyroxine sodium tablets when it fell below labeled potency during routine stability testing. Content analysis found the potency of the failed lot to be 85.5 percent to 86.2 percent.
Subsequently, an FDA inspection at the firm led to the issuance of a warning letter regarding the firm's levothyroxine sodium products. One of the deviations from good manufacturing practice regulations cited in that letter was failure to determine by appropriate stability testing the expiration date of some strengths of levothyroxine sodium. Another deviation concerned failure to establish adequate procedures for monitoring and control of temperature and humidity during the manufacturing process.
In April 1994, one manufacturer recalled seven lots of levothyroxine sodium products because potency could not be assured through the expiration date. In February 1995, the same manufacturer initiated a major recall of levothyroxine sodium affecting 60 lots and 50,436,000 tablets. The recall was initiated when the product was found to be below potency at 18-month stability testing.
In December 1995, a manufacturer recalled 22 lots of levothyroxine sodium products because potency could not be assured through the expiration date.
In addition to raising concerns about the consistent potency of orally administered levothyroxine sodium products, this pattern of stability problems suggests that the customary 2-year shelf life may not be appropriate for these products because they are prone to experience accelerated degradation in response to a variety of factors. Levothyroxine sodium is unstable in the presence of light, temperature, air, and humidity (Ref. 4).
One study found that some excipients used with levothyroxine sodium act as catalysts to hasten its degradation (Ref. 5).
In addition, the kinetics of levothyroxine sodium degradation is complex. Stability studies show that levothyroxine sodium exhibits a biphasic first order degradation profile, with an initial fast degradation rate followed by a slower rate (Ref. 4).
The initial fast rate varies depending on temperature. To compensate for the initial accelerated degradation, some manufacturers use an overage of active ingredient in their formulation, which can lead to occasional instances of superpotency."
Jeg fikk kommentarer på ovenstående på thyroid.about.com forumet, når jeg postet denne teksten som Mary Shomon har pp sin webside. De spurte om jeg var klar over hva Federal Registry var. Det er der alle lover og alt som er viktig og offisielt blir bokført i USA, det mest offisielle som fin i Amerika. "The document you quote is the Federal Register notice that declared all T4s marketed in the US to be unapproved drugs and in need of NDAs. It's a very significant document and should be required reading for all thyroid patients, in my honest opinion. (Since you're not in the US, you may not know that the Federal Register is the publication organ of the US government. If something's an official decision by any federal agency, it's published in the Federal Register.)"
I samme tidsrom ble det ikke rapportert om problemer med Thyroid.
Levothyroxine a new drug? Since when? How could that be? (man må betale for å lese denne)
"The US Food and Drug Administration (FDA) states that all approved levothyroxine sodium preparations should be considered therapeutically inequivalent unless equivalence has been established and noted in FDA's Approved Drug Products with Therapeutic Equivalence Evaluations (Orange Book)."
Hvordan tester man levothyroxin? Ikke på syke. Man gir friske høye doser og måler hvor høyt blodprøvene går:
"For pharmacokinetic studies designed to measure the bioavailability of LT4 formulations, the Food and Drug Administration (FDA)[8] recommends that a single dose be administered to healthy subjects at a strength several times the normal therapeutic dose.
The objective is to raise serum concentrations of the hormone sufficiently above endogenous baseline levels to achieve meaningful pharmacokinetic measurements."...
"The most recent clinical practice guidelines from the American Association of Clinical Endocrinologists (AACE) and the American Thyroid Association recognize that the various brands of LT4 have not been proven bioequivalent and recommend that the patient's brand not be changed during therapy.."
I denne studien brukte de data fra 31 friske mennesker som fikk en større dose thyroxin to ganger med 44 dagers mellomrom.
Mer om innovative drugs og generic drugs "In 1980, the FDA first published a list of approved drugs, consisting of innovator drugs approved through the NDA process and the generic products considered by the FDA to be therapeutically equivalent to these innovator products."
http://www.fda.gov/foi/warning_letters/g4190d.html (fins ikke lenger, er erstattet av ny warning) et eksempel av FDA warning om at man må søke om godkjenning
PDF om søknadsprosessen fra FDA
Brev til FDA fra Finland om Armour Thyroid
Om en pasient som foretrekker Armour Thyroid fremfor synthroid etc.
Her fra side 15 i denne linken hos findarticles.com:
Objections to the Use of Armour Thyroid
The main objections voiced in textbooks and editorials 1,73 regarding the use of desiccated
thyroid are: (1) its potency varies from batch to batch, and (2) the use of T3-containing preparations causes the serum T3 concentration to rise to supraphysiological levels.
Regarding between-batch variability, there may have been some problems with quality control a half-century or more ago, and in a 1980 study a number of generic versions of desiccated thyroid were still found to be unreliable in their potency. The amounts of T4 and T3 in Armour thyroid, on the other hand, were found to be constant.74
Moreover, two-year old tablets of Armour thyroid contained similar amounts of T4 and T3 as did fresh tablets. Three studies are typically cited to support the contention that T3 containing preparations should not be used. Smith et al reported a levothyroxine-plus-T3 product caused adverse side effects in 46 percent of patients; whereas, side effects occurred in only 10 percent of those receiving levothyroxine alone.75
In that study, however, the combination product and the levothyroxine product differed substantially in potency. For the combination treatment, each 100 mcg of levothyroxine was replaced by 80 mcg of levothyroxine plus 20 mcg of T3. Considering 20mcg of T3 is equivalent to 80 mcg of levothyroxine, the total hormone dose in the combination product was 60-percent greater than that in the levothyroxine preparation. Therefore, the high incidence of adverse side effects may not have been due to the T3, but to the higher total dose of thyroid hormones.
In the second study, by Surks et al, the administration of T3-containing preparations to
hypothyroid patients caused the plasma T3 concentration to become markedly elevated for several hours after ingestion of the medication.76
In most cases, however, the amount of T3 administered (50-75 mcg) was considerably greater than that contained in a typical dose of desiccated thyroid (9 mcg T3 per 60 mg),77 and/or the total dose of thyroid hormones given was excessive (180 mcg of levothyroxine plus 45 mcg of T3).
By contrast, in a patient given 60 mg of desiccated thyroid, the plasma T3 concentration increased from a hypothyroid level to a euthyroid level. Of two hypothyroid patients treated with 120 mg per day of desiccated thyroid, one showed a relatively constant plasma concentration of T3.
In the other patient, the T3 level increased by a maximum of 80 percent, to the bottom of the range seen in hyperthyroid patients, and returned to the baseline value within 24 hours. In that patient, the pre-dose plasma T3 concentration was near the top of the normal range, suggesting that this patient may have been receiving too high a dose of desiccated thyroid.
Finally, Jackson and Cobb reported that the serum T3 concentration (measured 2-5 hours
after a dose) was above normal in most patients receiving desiccated thyroid.2 They concluded there is little use for desiccated thyroid in clinical medicine. Most of the patients (87.5%) in that study, however, were taking a relatively large dose of desiccated thyroid (120-180 mg daily).
Moreover, 57.5 percent of the patients were not being treated for hypothyroidism, but rather to suppress the thyroid gland. Nearly half of the patients continued to have an elevated serum T3 concentration after they were switched to levothyroxine, even though the equivalent dose was reduced in 62.5 percent of patients.
Thus, the elevated serum T3 concentrations found in this study can be explained in large part by the high doses used and by the selection of patients, the majority of whom
were not hypothyroid. What this study does suggest is that desiccated thyroid should not be used for thyroid-suppression therapy.
Although the oral administration of T3 causes a transient increase in serum T3 concentrations, that fact does not appear to be of significance for hypothyroid patients receiving usual replacement doses of Armour thyroid. In this author's experience, reports of post-dose symptoms of hyperthyroidism are extremely rare, even among patients taking larger doses of desiccated thyroid.
An occasional patient reports feeling better when he or she takes Armour thyroid in two divided doses daily. The nature of that improvement, however, is usually an increase in effectiveness, rather than a reduction in side effects.
For patients taking relatively large amounts of desiccated thyroid (such as 120 mg daily or more), splitting the daily dose would obviate any potential concern about transient elevations of T3 levels. In practice, however, splitting the daily dose is rarely necessary.
En søkemotor for artikler: http://www.unboundmedicine.com/medline/ebm/mesh/Thyroid_Gland,_Desiccated
Comments