hypothyroidism

• common causes of primary hypothyroidism include: 1)Chronic autoimmune thyroiditis 2)post-surgery 3)post radio-active iodine
• any cause of anterior hypopituitarism lead to secondary hypothyroidism
• investigations: in primary hypothyroidism TSH levels are elevated and t4 levels are low.. we will have to take blood and check for cortisol and ACTH levels, if cortisol is low give hydrocortisone replacement before starting levothyroxine
• medicine treatment: 1)Give levothyroxine,oral,100mcg daily. 2)if the payient has risk of IHD,start the dose of levothyroxine with 25mcg daily and increase dose every 4 weeks by 25mcg
• once the patient is on treatment,check TSH and T4 levels after 2-3months. TSH takes several weeks to stabilize. once t4 and TSH levels are stabilised, checks the levels every year
• hypothyroidism in pregnancy: hypothyroid pregnant women need an increase in the dose of levothyroxine therapy especially 2nd and 3rd semester. is is advisable to incraese dose by 30%, then after delivery get back to original dose
• we have primary and secondary hypothyroidism
• in primary hypothyroidism: 1)follicular thyroid cells are damaged-less thyroglobulin production 2)iodine deficiency.
• in primary hypothyroidism there is high levels of TSH and low levels of T3 & T4
• causes of primary hypothyroidism-thyroid destruction:A. autoimmune -1)Hashimoto 2)postpartum 3)Riedels-fibrotic thyroid B. infectious- 1)DeQuervains C. Iatrogenic- 1)thyrodectomy 2)wolff-chaikoff effect
• Hashimoto-inflammation of thyroid: this form anti-TG and anti-TPO antibodies and happens in young people with mutation of HLA DR3 and HLA DR4. they usually have diabetes and hypothyroidism here is permanent
• postpartum hypothyroidism: usually happens after 1 year of birth of a child and the postpartum trigger antibodies TPO-but this is not chronic ,this is a transient hypothyroidism
• Riedels hypothyroidism: form IgG4 antibodies that activate fibroblasts therefore fibroous tissue will be release leading to fibrosis of the thyroid gland. fibrosis causes compression of trachea,laryngeal nerve leading to hoarseness,dyspnea and dysphagia-difficult swallowing
• riedels is also associated with autoimmune pancreatitis and aortitis
• infectious thyroiditis is triggered by viral upper resporatory tract infection very painful thyroid goiter,elevated ESR and this is a transient hypothyroidism-signs include headache,sore throat,fever mayalgia
• secondary hypothyroidism: the damage is on hypothalamas or pituitary gland therefore there is low levels of TSH and low levels of t3 and t4
• causes of secondary hypothyroidism include: Pituitary adenoma and sheehan syndrome-loosing too much blood that deprive the pituitary gland from working properly
• so in pituitary adenoma the tumor is too big that it compresses hypophyseal system where TRH pass. if TRH cannot reach anterior pituitary there will be no stimulation of TSH leading to low tsh. this compression lead to headache and bitemporal hemianopia-compressed opric chiasma
• sheehan syndrome occurs after too much bleeding,now there is less perfusion to the pituitary gland,leading to ischaemia-death of cells ,now TSH cannot be produced