Hypothyroidism
Diseases

Author: piredda laura
Date: 06/05/2009

Description

DEFINITION

Hypothyroidism is a morbid condition caused by a lack of thyroid hormones (T3 and T4) or a lack of their effect on target tissues (TH resistance).

The disease definition according to a specific consensus conference or to The Diseases Database based on the Unified Medical Language System (NLM)

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Wikipedia"URL":
The Diseases Database"URL":
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EPIDEMIOLOGY

The hypothyroidism is commonly in the elderly. The increased frequency is observed in women. Prevalence over 60 years is the 1.5-2%.
It may already be present at birth and determine, if not promptly treated, serious problems of intellectual and physical development (cretinism sporadic), now easily preventable through the tests that are found all the babies to see if their thyroid is well developed during the pregnancy and especially function normally at birth (neonatal screening of hypothyroidism)
Thanks to improved social conditions and health, a diet richer and more balanced - even with the use of iodized salt (iodine prophylaxis) - Neonatal screening and advances in the diagnosis and treatment of thyroid diseases, today these serious forms of hypothyroidism in early childhood onset are actually missing.
Remains very frequently hypothyroidism in:

  • children of school age
  • adolescents
  • adults

In these cases the hormonal deficiency appears in a body already more or less fully developed, particularly in the brain, and therefore does not give cretinism. Are present goiter other disorders more or less severe. If not properly treated, hypothyroidism can impair the efficiency of the whole body.
The disease is found:

  • Europe
  • North America
  • Nepal
  • New Guinea
  • Zaire

In some countries, including Italy, hypothyroidism from lack of iodine in the diet is still quite common, even in children and adolescents. Over 10 million Italians are suffering because of goiter endemic iodine deficiency. One problem not yet solved, so that was recently approved by Parliament a law to encourage the consumption of iodized salt in place of common table salt. The use of salt enriched with iodine in the preparation and storage of foods is an effective form of prophylaxis of endemic goiter.

SYMPTOMS

Symptoms affect all the organs because they are all
sensitive to hormone (Symptoms)

In some ways the most serious one has the so-called facies myxedematosa, resulting in swelling of the face and is due mainly to an increase of interstitial fluid in skin tissue.
The myxedema is a hard swelling which can affect:

  • mouth (swelling)
  • vocal cords (deterioration of the voice becomes throaty)
  • skin and appendages (hair loss, dry skin)
  • yellowing of the skin (palms of the hands and soles of the feet).
  • goitre may be present, if the cause is due to an altered synthesis of thyroid hormones, for example, to lack of iodine. In some patients the goitre disorders may give local compression, especially if you have retrostenal extension. In this case you can have compression and displacement of the trachea or esophagus, the patient complains of difficulty swallowing solid foods.

Myxedema coma

It’s a serious medical condition that appears rarely, is exceptionally the final stage of hypothyroidism, occurs most often after prolonged exposure to cold, infections and trauma, or following ingestion of sedative drugs.
Symptoms:

  • slowed heart rate
  • hypothermia (body temperature below 34 ° C)
  • somnolence gradually until coma.
  • cardiomegaly
  • bradycardia
  • abnormalities of the genital tract, with decreased libido in men and women, and abnormal menstrual cycle
  • muscle fatigue
  • alterations of the skeleton (hypothyroidism occurs during childhood)

DIAGNOSIS

The symptoms are not sufficient to make diagnosis, but must be used at a dose of thyroid hormones.
Laboratory tests:

  • thyroid hormone dosing: FT3 and FT4 (reduced); thyrotropin, TSH (increased)
    In patients where there is evidence of low FT4 and normal or low TSH, you should seek a secondary hypothyroidism with interest then of hypothalamus and pituitary. In this case the tests are made more complicated, one of which is the Test to TRH
  • antithyroid antibodies: antithyreoglobulin and antiperoxidase to search for an autoimmune involvement, as in thyroiditis.
  • complete blood count:hypercholesterolemy, anaemia (reduction of hemoglobin values)

PATIENT RISK FACTORS

Vascular

Genetic

Acquired

Hormonal

Genetic

Acquired

TISSUE SPECIFIC RISK FACTORS

anatomical (due its structure)

vascular (due to the local circulation)

physiopathological (due to tissue function and activity)

PATHOGENESIS

The system includes hypothalamus -> pituitary -> thyroid -> liver -> receptors
tissue (muscle, liver, heart etc) any alteration in one of these points induces different disease:

  • hypothalamus and pituitary
    • mutated gene for the hypothalamic receptor -> thyroid hormones act through negative feedback on hypothalamus and pituitary tying a subtype of THRB that could be mutated
    • levels of thyroid hormones slightly subnormal -> increase secretion of TSH from the pituitary gland
    • lesion -> hormone insufficient respectively TRH and TSH hormone, resulting in reduced incentives for the production of thyroid hormones (secondary hypothyroidism)
  • thyroid
    • development of congenital deficiency of thyroid gland -> at birth there is a reduced mass of thyroid tissue; during fetal life and neonatal deficiency of thyroid hormones causes a developmental delay of the central nervous system
    • autoimmune processes -> body due to an infection of the thyroid (Hashimoto thyroiditis) produces antibodies against its own thyroid tissue. The thyroid gland becomes fibrotic and has a low volume, the synthesis function is impaired.
    • post-treatment -> reduction of thyroid tissue due to thyroid surgery or radiation therapy with radio-iodine, used in hyperthyroidism; also use of drugs antithyroid
    • iodine deficiency, or intake of high amounts of iodine in the form of drugs (it's content, for example, in the cough syrups) or dietary supplements.
    • selenium deficiency
    • changes in the proteins necessary for synthesis of biochemical processes of thyroid hormones
  • lack of conversion of T4 to T3 in the liver, but is not documented in humans or animals. Low T3 with normal T4 values are often due to concomitant disease (euthyroid syndrome) or administration of drugs:
    • amiodarone
    • lithium
    • propranolol
    • corticosteroids
    • contrast media iodates

COMPLICATIONS
Complications

TREATMENT

Thyroid Hormone Replacement Therapy

Patients info

Hypothyroidism overview at endocrineweb
Laura Piredda e Marzia Pera

Comments
2016-10-19T13:40:34 - Gianpiero Pescarmona

Common chemicals that can induce hypothyroidism

HYPOTHYROID AND AUTONOMIC CHANGES--ROLE OF MEDULLARY TRH, 1995

The proposed studies will provide evidence that thyroid hormone may act directly on the medullary nuclei related to autonomic function by regulating the synthesis and turnover of its neuropeptides and neurotransmitters and will yield substantive information on the mechanisms through which autonomic disorders participate in the clinical manifestations of thyroid diseases.

Small non-coding RNAs in animal development 2008

In normal conditions in wild-type animals, miR-208 maintains an optimal level of the thyroid hormone receptor (TR) cascade activity by acting on THRAP1 (thyroid hormone receptor-associated protein complex 240 kDa component) in a negative feedback loop. In transgenic mice that overexpress miR-208, inhibition of the TR pathways allows aberrant expression of beta-myosin heavy chain (betaMHC) in the adult. Similarly, in conditions of stress or hypothyroidism, decreased activity of the TR cascade leads to expression of betaMHC and hypertrophy. In the absence of miR-208 in null mice, THRAP1 is de-repressed and baseline levels of TR activity are abnormally high and resistant to inhibition by stress signals. Therefore, Mir-208-null mice do not express elevated levels of betaMHC or undergo cardiac hypertrophy in conditions of stress and hypothyroidism. T3, tri-iodothyronine; TRE, T3 response element.

Approach to mild hypothyroidism diagnosis

L'ipotiroidismo in Italia
L'ipotiroidismo congenito in Italia, 2009,Meeting ISS

DHEA albumin in hypothyroidism

Serum Dehydroepiandrosterone, Dehydroepiandrosterone Sulfate, and Pregnenolone Sulfate Concentrations in Patients with Hyperthyroidism and Hypothyroidism 2000

Effects of developmental hypothyroidism induced by maternal administration of methimazole or propylthiouracil on the immune system of rats. 2007

Endocrinologia-tiroide
Anemia, ipotiroidismo subclinico e levotiroxina
I pazienti con anemia da deficit di ferro ed ipotiroidismo subclinico potrebbero richiedere il trattamento con ferro e levotiroxina. Vi � infatti una categoria di pazienti che non risponde bene al ferro per via orale proprio a causa della concomitante presenza di ipotiroidismo subclinico, e questi pazienti potrebbero trarre beneficio dall'integrazione della levotiroxina. In generale, questa condizione si osserva nel 17,2 percento dei casi. Gli ormoni tiroidei hanno un effetto diffuso nell'organismo, e minore � il livello dell'emoglobina, maggiore � l'effetto della combinazione ferro-levotiroxina. E' stato dimostrato anche che bench� la levotiroxina aumenti i livelli di eritropoietina, essa non incrementa quelli dell'emoglobina nei pazienti con ipotiroidismo subclinico non anemici. Sembra dunque che l'interazione fra ormone tiroideo, tireotropina e cellule non sia semplicemente un'estensione dei loro effetti fisiologici, ma che questi ormoni abbiano effetti d'organo unici sia a livello sistemico che cellulare, probabilmente sulla base dello status di deficit o eccesso. Sono in programma studi per investigare l'effetto di elementi quali selenio e zinco nel trattamento dei pazienti con ipotiroidismo subclinico e deficit di ferro. (J Clin Endocrinol Metab 2009; 94: 151-6)

Gastroenterologia
Ipotiroidismo e tumori epatici nelle donne
Le donne con ipotiroidismo di vecchia data presentano un aumento del rischio di carcinomi epatocellulari, mentre ci� non si riscontra nel sesso maschile. E' noto che gli ormoni tiroidei sono coinvolti nel metabolismo lipidico, e vi sono prove di un legame fra ipotiroidismo e steatoepatite non alcolica, ma non era finora chiaro se i disordini della tiroide fossero associati ai tumori epatici. Sono ora necessari studi in popolazioni diverse per confermare l'associazione fra ipotiroidismo e carcinoma epatocellulare ed identificare i meccanismi biologici di base ed i fattori predisponenti che potrebbero contribuire alla suscettibilit� a questi tumori in presenza di disordini tiroidei. (Hepatology 2009; 49: 1563-70)

Endocrinologia
Rapporto tra ipotiroidismo, diabete e mortalit� Cv
L'ipotiroidismo subclinico (Is) � stato associato a una maggiore prevalenza di malattia cardiovascolare ed � di riscontro comune in pazienti con diabete di tipo 2 (Dm). Per indagare la veridicit� di questi dati clinici, � stata condotta un'ampia analisi retrospettiva su 6.540 soggetti, di cui 472 affetti da Dm e con un aumentato livello di Tsh, paragonati con 472 soggetti di pari et� con Dm e normali valori di Tsh. La relazione tra Is e mortalit� cardiovascolare � stata effettuata mediante regressione logistica. Si sono registrati 222 nuovi eventi cardiovascolari nei pazienti con Is rispetto a 246 eventi in pazienti senza. E si sono avuti 96 morti da tutte le cause nei pazienti con Is rispetto a 155 in quelli senza. Non si � avuta alcuna relazione tra il valore di Tsh iniziale e la mortalit� cardiovascolare. Nel complesso, i pazienti con Is e Dm non avevano una mortalit� cardiovascolare accresciuta rispetto ai pazienti con Dm senza Is. Inaspettatamente, si � avuta una riduzione significativa della mortalit� da ogni causa nei pazienti con Is e Dm. Questi dati sono in accordo con studi che mostrano che individui anziani con pi� alti livelli di Tsh hanno dimostrato una vita prolungata. In conclusione, l'Is pu� avere un effetto protettivo sulla mortalit� non-cardiovascolare nel Dm.

Diabetes care, 2010;33(3):e37

vitamin d eosinophils

vitamin d hypothyroidism

Diurnal hormone-metabolite profiles in hypothyroidism. 1981

Fasting blood lactate and pyruvate levels were normal but post-prandial hyperlactataemia and hyperpyruvicaemia were found and mean 12 h values for lactate (hypothyroid 1.80 +/- 0.06 v. control 0.77 +/- 0.03 mmol/l, P less than 0.01) and pyruvate (0.10 +/- 0.01 v. 0.08 +/- 0.003 mmol/l, P less than 0.01) were elevated.

Goiter iron deficiency - Results from Quertle®

Are human herpes viruses associated with autoimmune thyroid disease?

  • INTRODUCTION Autoimmune diseases are complex diseases with genetic, endogenous and environmental etiologies. Viral infections have been postulated as one of the factors that may be the trigger of autoimmune diseases.
    METHODOLOGY Thyroid peroxidase (TPO) and thyroglobulin (TG) antibodies were measured before thyroidectomy in 100 subjects by chemiluminescence method, 50 of whom were autoimmune thyroid diseases (AITD) patients and 50 of whom were multinodular goiter (MNG) patients used as a control group. Fresh thyroid samples were collected from all 100 subjects after thyroidectomy to investigate the DNAs of herpes simplex viruses types 1 and 2 (HSV-1, HSV-2), Varicella Zoster virus (VZV), Epstein-Barr virus (EBV), Cytomegalovirus (CMV) and human herpes virus type 6 (HHV-6) by PCR.
    RESULTS The DNA of HSV-1, HSV-2, VZV, EBV, CMV and HHV-6 were detected in neither the patient group nor in the control group. The mean values of anti-TPO and anti-TG antibodies ranged within 9.5-2000 units/ml (527.8 ± 617.4) and 108-5000 units/ml (1458.2 ± 1774.1) in the AITD patients group, respectively. A statistically significant difference of the mean level of anti-TPO and anti-TG antibodies among the two groups was found (p value < 0.05).
    CONCLUSIONS The possible role of human herpes viruses in the pathogenesis of AITD is not supported by our study; hence our raised question stays open for more investigation on more patients and in different parts of the country using different sizes and sites of biopsies.
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