hypothyroidism
TRANSCRIPT
HypothyroidismCauses of dryness and thickness of skin
obesity
Congenital and autoimmune
By Mahdi Saleh
Autoimmune Disorder
OfHypothyroidism
Hashimoto disease
Autoimmune Disorder Of Thyroid Gland
Hashimoto Thyroiditisis an autoimmune disease that results in destruction of the thyroid gland and gradual and progressive thyroid failure.
The condition was named after Dr. Hakaru Hashimoto, the doctor
who described it in 1912.
Autoimmune Disorder Of Thyroid Gland
Hashimoto ThyroiditisIt is the most common cause of hypothyroidism in areas of the world where iodine levels are sufficient.
Autoimmune Disorder Of Thyroid Gland
Hashimoto ThyroiditisIt is most prevalent:
45 and 65 yearsmore common in womencan also occur in children 45-65
Autoimmune Disorder Of Thyroid Gland
CD8+ cytotoxic T cell-mediated cell death :CD8+ cytotoxic T cells may destroy
thyroid follicular cells.
Autoimmune Disorder Of Thyroid Gland
Cytokine-mediated cell death: Activation of CD4+ T cells leads to the production of inflammatory cytokines such as interferon-γ in the thyroid gland, with resultant recruitment and activation of macrophages and damage to follicles.
Autoimmune Disorder Of Thyroid Gland
A less likely mechanism involves binding of antithyroid antibodies (antithyroglobulin, and antithyroid peroxidase antibodies) followed by antibody-dependent cellmediated cytotoxicity
Autoimmune Disorder Of Thyroid Gland
For more information look at:Robbins and Cotran PathologyChapter 24 page 1085-1088
Congenital Of
Hypothyroidism
Introduction To Thyroid Embryology
congenital cusses
Introduction To Thyroid Embryology
The thyroid gland appears as an epithelial pro- liferation in the floor of the pharynx between the tuberculum impar and the copula at a point later indicated by the foramen cecum
Introduction To Thyroid Embryology
Subsequently, the thyroid descends in front of the pharyngeal gut as a bilobed diverticulum During this migration, the thyroid remains connected to the tongue by a narrow canal, the thyroglossal duct. This duct later disappears.
Introduction To Thyroid Embryology
the thyroid gland descends in front of the hyoid bone and the laryn- geal cartilages. It reaches its final position in front of the trachea in the seventh week
Congenital Disorder Of Thyroid Gland
Congenital hypothyroidism is a partial or complete loss of function of
the thyroid gland (hypothyroidism) that affects infants from birth (congenital)
Congenital Disorder Of Thyroid Gland
ectopic thyroid gland
Dyshormonogenesis TSHR mutation
ectopic thyroid gland
Ectopic thyroid is a developmental defect of thyroid gland that leads to presence of thyroid tissue at sites other than its normal cervical location. It is frequently found along the course of the thyroglossal duct. Lingual thyroid is the most common presentation of ectopic thyroid
TSHR mutation
The TSHR gene provides instructions for making a protein, known as a receptor, that binds to a thyroid stimulating hormone (TSH). This receptor spans the membrane of certain cells (called follicular cells) in the thyroid gland. A large part of the receptor sits on the outer surface of the cell (extracellular), and a small portion is retained inside the cell (intracellular). Thyroid stimulating hormone binds to the extracellular portion of the receptor, activating a series of reactions that control
development of the thyroid gland and its functions .
TSHR mutation
Several TSHR gene mutations have been identified in people with congenital hypothyroidism . TSHR gene mutations change one of the protein building blocks (amino acids) used to make the TSHR. Some of these mutations prevent the receptor from properly spanning the membrane, and in some cases the entire receptor is retained inside the cell. As a result, the receptor cannot interact properly with thyroid stimulating hormone. Other mutations impair the receptor's ability to bind with thyroid stimulating hormone, even though the receptor correctly spans the membrane.
TSHR mutation
Without properly functioning receptors, thyroid hormone production is not stimulated. The body tries to correct the blocked stimulation by producing more TSH . In some cases, the increased levels of TSH compensate for receptors with minor defects, and the thyroid functions normally. In other cases, thyroid hormone levels remain low, causing mild to severe congenital hypothyroidism. Impaired thyroid stimulating hormone receptors may also disrupt thyroid development, and as a result, the gland is smaller than normal. Cases of congenital hypothyroidism caused by TSHR gene mutations are sometimes classified as thyroid dysgenesis because development of the thyroid gland is impaired.
Dyshormonogenesis
is a type of primary congenital hypothyroidism, a permanent
thyroid hormone deficiency that is present from birth, which results
from inborn errors of thyroid hormone synthesis.
For more information look at:
Langman’s Medical EmbryologyChapter 17page 292-294
skin and
Hypothyroidism
Hashimoto disease
Effect Of Thyroid On Skin
Too much thyroid hormone , and skin can become warm, sweaty and flushed .
Too little thyroid hormone , and skin becomes dry, coarse, thick and even sweating is
decreased .Thyroid dysfunction can also lead to thinning hair and eventual hair loss.
Hypothyroidism Skin
In hypothyroidism there is a slow metabolic rate due to alteration of glandular function. The slowed metabolic function results in insidious onset of tiredness, fatigue, leg cramps, etc. The skin is cold, dry and pale. The dryness can be extreme so that there is no sweating and the palms and soles get thick and dry (keratoderma).The skin colour can be yellow due to alteration in Vitamin A metabolism carotenemia.
Hair is lost all over - scalp, groin, even lateral eyebrows. Nails grow slowly and are brittle and thick.
The most common skin change is a generalized myxedema or swelling due to a build up of ground substance in the foundation of the skin (dermis). The skin is swollen, dry, pale and waxy. One can slowly develop a broad nose, swollen lips and puffy eyelids. Wounds heal slowly
obesity and
Hypothyroidism
Relationship between weight and thyroid
Decreased Body Weight. A greatly increased amount of thyroid hormone almost always decreases body weight, and a greatly decreased amount of thyroid
hormone almost always increases body weight; however, these effects do not always occur
because thyroid hormone also increases the appetite, which may counterbalance the change in
the metabolic rate.
Basal Metabolic Rate (BMR).
BMRs are associated with changes in energy balance
Energy balance reflects the difference between the amount of calories one eats and the amount of
calories the body useshigh BMR weight loss
Relationship between weight and thyroid
The BMR in the patient with hypothyroidism is decreasedThe weight gain not always related to excess fat accumulation. Most of the extra weight gained in hypothyroid individuals is due to excess accumulation of salt and water.
Guyton And Hall Medical PhysiologyChapter 77page 956-963
For more information look at:
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