Hypothyroidism

Hypothyroidism[]

Hypothyroidism is a condition in which there is a reduction of thyroid hormone.This condition is often called underactive thyroid.

The thyroid gland is part of the endocrine system. It is located at the front of the neck, a little above where the collarbones meet. Thyroid hormone is an essential regulator of almost every cell in the human body.Thyroid hormone binds to specific nuclear regulators on DNA of the cells and activates unique transcription, thereby regulating metabolic and developmental functions ( Brent, et. al, 2011)

Thyroid hormone is comprised of T3 and T4; the thyroid secretes both. Most T3 and T4 are bound to thyroid binding globulin (TBG), which is a type of secondary regulator of the activity thyroid hormone. When the hormone is bound to TBG, its inactive. Therefore, T3 and T3 that are not bound to thyroid binding globulin are referred to as “free” T3 or T4. The T3 and T4 are the metabolically hormone,T3 is more active than T4, but the two can be interconverted. The concentrations of T4 and T3 in the serum are continually monitored by their concentrations in the anterior pituitary. Production of TSH termed thyrotropin is inversely related to the intra-pituitary concentration of T3. Also, the sensitivity and responsiveness of the pituitary cells are regulated by tripeptide, hypothalamic hormone called thyrotropin releasing hormone (TRH), delivered directly by the pituitary portal circulation from the hypothalamus ( Brent, et al, 2011)

Feedback Control[]

The hypothalamus, pituitary and thyroid are controlled by a negative feedback mechanism. The hypothalamus continually secretes Thyrotropin-Releasing-Hormone (a tri-peptide :pyro-Glu-His-Pro) into the portal venous supply of the anterior pituitary. TRH maintains responsiveness of the pituitary thyrotrophs; change the glycosylation and biological effectiveness of TSH. The thyrotrophs deiodinate intrapituitary T4 to pituitary T3, which inhibits production and secretion of TSH by the thyrotrophs. In addition, an increase in T3 in the hypothalamus inhibits the gene for production of TRH. TRH induces the release of prolactin as well, thus hyperprolactinemia can be found in patients with primary hypothyroidism.

Primary hypothyroidism-decreased thyroid hormone due to decreased production by the thyroid. High TSH, means low T3 and T4, due to decrease inhibitory feedback on the hypothalamus and anterior pituitary.T4 and T4 normally cause the TSH production to go down and so low T3 and T4 and high TSH is characteristic of primary hypothyroidism.

Secondary and tertiary hypothyroidism is as a result of decreased thyroid hormone due to decreased stimulation of the thyroid. This decreased stimulation could be as a result of decrease TSH (secondary) or Thyrotropin releasing hormone or TRH (tertiary). TRH comes from the hypothalamus and stimulates the production of TSH; TSH comes from the anterior pituitary and stimulates the thyroid to produce thyroid hormones. A decreased TSH will occur in both secondary and tertiary hypothyroidism; but decrease TRH would occur in tertiary hypothyroidism

Causes/Symptoms[]

The most common cause of hypothyroidism is thyroiditis (inflammation of the thyroid gland's cells).The immune system attacking the thyroid gland. Viral infections (common cold) or other respiratory infections. Pregnancy (often called postpartum thyroiditis)

symptoms:

Hard stools or constipation
Increased sensitivity to cold temperature.
Fatigue. Joint or muscle pain, weight gain
Heavier and irregular menstrual periods
Paleness or dry skin. Thin, brittle hair or fingernails
Sadness or depression
Fatigue
Goiter
obesity,
infertility, heart disease
etc

rs7850258[]

Research has shown that "rs7850258 a SNP http://www.ncbi.nlm.nih.gov/snp/?term=rs2517532 in the FOXE1 gene had 1.35 times higher odds of having primary hypothyroidism compared to those with the AG genotype, and those with the AA genotype had 0.74 times the odds of developing the condition" (23andMe, 2014). Prof. Burk happens to be among the individual with AG genotype and has a lower predisposition of developing primary hypothyroidism.It will be reasonable to consult the advice of a trained medical professional now or in the near future.

Treatment[]

Thyroid hormone pills. Levothyroxine is the most commonly used medication or Surgery

References[]

Brent GA, Davies TF. Hypothyroidism and thyroiditis. In: Melmed S, Polonsky KS,Larsen PR, Kronenberg HM, et al. Williams Textbook of Endocrinology.12th ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 13, page 362-84.

Denny JC et al. (2011). “Variants Near FOXE1 Are Associated with Hypothyroidism and Other Thyroid Conditions: Using Electronic Medical Records for Genome- and Phenome-wide Studies.” Am J Hum Genet 89(4):529-42.http://www.ncbi.nlm.nih.gov/pubmed?cmd=Search&term=21981779

Eriksson N et al. (2012) . “Novel Associations for Hypothyroidism Include Known Autoimmune Risk Loci” PLoS ONE e34442 http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0034442