Endocrinology Flashcards
What happens to thyroxine-binding globulin (TBG) levels during pregnancy?
There is an increase in TBG levels during pregnancy.
This increase causes an increase in total thyroxine levels but does not affect free thyroxine levels.
What are the risks associated with untreated thyrotoxicosis in pregnancy?
Untreated thyrotoxicosis increases the risk of:
* fetal loss
* maternal heart failure
* premature labour
These complications can have serious implications for both the mother and the fetus.
What is the most common cause of thyrotoxicosis in pregnancy?
Graves’ disease is the most common cause of thyrotoxicosis in pregnancy.
Activation of the TSH receptor by HCG may also occur, termed transient gestational hyperthyroidism.
What is the traditional antithyroid drug of choice in pregnancy?
Propylthiouracil has traditionally been the antithyroid drug of choice.
However, it is associated with an increased risk of severe hepatic injury.
When is propylthiouracil generally used during pregnancy?
Propylthiouracil is generally used in the first trimester of pregnancy.
It is used in place of carbimazole due to carbimazole’s association with congenital abnormalities.
What should maternal free thyroxine levels be kept at during pregnancy?
Maternal free thyroxine levels should be kept in the upper third of the normal reference range.
This is to avoid fetal hypothyroidism.
When should thyrotrophin receptor stimulating antibodies be checked during pregnancy?
Thyrotrophin receptor stimulating antibodies should be checked at 30-36 weeks gestation.
This helps to determine the risk of neonatal thyroid problems.
What management strategies should not be used in pregnancy?
Block-and-replace regimes should not be used in pregnancy.
Additionally, radioiodine therapy is contraindicated.
Is thyroxine safe during pregnancy?
Yes, thyroxine is safe during pregnancy.
It is important for maintaining proper thyroid function.
How often should serum thyroid-stimulating hormone be measured during pregnancy?
Serum thyroid-stimulating hormone should be measured in each trimester and 6-8 weeks post-partum.
This monitoring ensures appropriate thyroid hormone levels are maintained.
How much of an increased dose of thyroxine do women require during pregnancy?
Women require an increased dose of thyroxine during pregnancy by up to 50% as early as 4-6 weeks of pregnancy.
This adjustment is critical for both maternal and fetal health.
Is breastfeeding safe while on thyroxine?
Yes, breastfeeding is safe while on thyroxine.
Thyroxine does not pose a risk to the breastfeeding infant.
what is Gitelman’s syndrome?
Gitelman’s syndrome is due to a defect in the thiazide-sensitive Na+ Cl- transporter in the distal convoluted tubule.
What are the features of Gitelman’s syndrome?
normotension
hypokalaemia
hypocalciuria
hypomagnesaemia
metabolic alkalosis
what causes acromegaly?
In acromegaly there is excess growth hormone secondary to a pituitary adenoma in over 95% of cases. A minority of cases are caused by ectopic GHRH or GH production by tumours e.g. pancreatic.
what are the features of acromegaly?
coarse facial appearance, spade-like hands, increase in shoe size
large tongue, prognathism, interdental spaces
excessive sweating and oily skin: caused by sweat gland hypertrophy
features of pituitary tumour: hypopituitarism, headaches, bitemporal hemianopia
raised prolactin in 1/3 of cases → galactorrhoea
6% of patients have MEN-1
What are the complications of acromegaly?
hypertension
diabetes (>10%)
cardiomyopathy
colorectal cancer
what is a contraindication to piaglitazone?
heart failure
what are thiazolidinediones?
Thiazolidinediones are a class of agents used in the treatment of type 2 diabetes mellitus. They are agonists to the PPAR-gamma receptor and reduce peripheral insulin resistance.
Pioglitazone is a thiazolidinedione
What are adverse effects of thiazolidinediones?
weight gain
liver impairment: monitor LFTs
fluid retention - therefore contraindicated in heart failure. The risk of fluid retention is increased if the patient also takes insulin
recent studies have indicated an increased risk of fractures
bladder cancer: recent studies have shown an increased risk of bladder cancer in patients taking pioglitazone (hazard ratio 2.64)
what is hashimoto’s thyroiditis?
Hashimoto’s thyroiditis (chronic autoimmune thyroiditis) is an autoimmune disorder of the thyroid gland. It is typically associated with hypothyroidism although there may be a transient thyrotoxicosis in the acute phase. It is 10 times more common in wome
Features of Hasimoto’s thyroiditis?
features of hypothyroidism
goitre: firm, non-tender
anti-thyroid peroxidase (TPO) and also anti-thyroglobulin (Tg) antibodies
Associations with Hashimoto’s thyroiditis?
other autoimmune conditions e.g. coeliac disease, type 1 diabetes mellitus, vitiligo
Hashimoto’s thyroiditis is associated with the development of MALT lymphoma
what can Raised total T3 and T4 but normal fT3 and fT4 suggest?
Raised total T3 and T4 but normal fT3 and fT4 suggest high concentrations of thyroid binding globulin, which can be seen during pregnancy
Elevated oestrogen levels produced in pregnancy stimulate the expression of thyroid binding globulin (TBG) from the liver. As TBG binds to free thyroxine (fT4) and free triiodothyronine (fT3), an increase in TBG results in an initial lowering of fT4 and fT3. This in turn causes a secondary increase in thyroid-stimulating hormone (TSH). The net result is a new equilibrium between free and bound thyroid hormones with an increase in bound-T3 and T4 but an overall unaffected fT3 and fT4 level. As it’s the fT4 and fT3 that are responsible for clinic features of thyrotoxicosis these cases rarely produce clinical signs or symptoms, nor do they require treatment.