Thyroid disease

-the second most common endocrine disorder affecting women of reproductive age. -The thyroid gland comprises two lobes connected by the isthmus. - Follicular cells within the lobes produce the thyroid hormones. Thyroxin (T4) and tri- iodothyronine (T3) -these hormones are iodine-containing hormones, which are essential for normal body growth in infancy and childhood and affects the metabolic rate of the body.

The thyroid gland also produces calcitonin, which is required for calcium metabolism. -The production and release of T3 and T4, is regulated by thyroid-stimulating hormone (TSH), which is secreted by the anterior pituitary gland. -Production of the thyroid hormones depends on dietary consumption of iodine and calcium

- After digestion and synthesis the thyroid hormones become bound with protein called thyroid-binding globulin (TBG) & stored within the thyroid. -Stored thyroid hormone is capable of supplying the body with the required amount of hormone for 2–3 months. -In pregnancy, hypothalamic and pituitary regulation maintain normal levels of TSH; however, thyroid function is affected by four factors

1-Oestrogen stimulates the production of TBG 2 -Human chorionic gonadotrophin (HCG) secreted by the placenta. 3-A rise in the glomerular filtration rate in pregnancy leads to increased renal clearance of iodine, resulting in an increase in dietary iodine requirement. 4 The fetal thyroid begins concentrating iodine at 10–12 weeks' gestation and is controlled by fetal pituitary TSH by approximately 20 weeks' gestation. Fetal levels will be dependent on maternal levels of iodine.

-Clinical assessment of thyroid dysfunction is difficult as pregnancy-related symptoms are similar to hyperthyroidism and hypothyroidism. -Thyroid function can be assessed by biochemical tests that measure, free thyroxin (FT4), free T3 (FT3) and TSH

Hyperthyroidism -(also called thyrotoxicosis) -The most common cause of hyperthyroidism in pregnancy is Graves' disease. - This is an autoimmune disorder -The gland becomes enlarged and secretes an increased amount of thyroid hormone. -The metabolic processes of the body are accelerated resulting in

- sweating - tachycardia -dyspnoea - diarrhea -mood lability -and fatigue

-Maternal and fetal complications include: 1- miscarriage 2- placenta abruption 3- pre-term labour and birth 4-pre-eclampsia 5- intrauterine growth restriction

thyroid storm: is A serious complication of untreated or poorly controlled hyperthyroidism. -This may occur spontaneously or be precipitated by: 1-infection 2- surgery 3-stress such as labour and birth. - It is characterized by signs and symptoms associated with an extreme hyper metabolic state:

hyperthermia (>41 °C) leading to dehydration, tachycardia, acute respiratory distress and cardiovascular collapse. Intervention of thyroid storm : a medical emergency requiring 1- the administration of oxygen 2- use of antipyretics 3- cooling blanket 4- hydration 5- antibiotics 6- drug therapy to stop the production and reduce the effect of thyroid hormone

- complications of Thyroid storm: 1- maternal heart failure 2- fetal or neonatal hyperthyroidism 3- stillbirth.

Treatment 1-antithyroid medication. Propylthiouracil (PTU), 2-methimazole 3- carbimazole -PTU is the drug of choice as less of it crosses the placenta and only small amounts are found in breast milk. -The aim of treatment is to use the lowest dose possible as these drugs may cause goiter and hypothyroidism in the fetus.

During childbirth the midwife should be aware of factors that may precipitate thyroid storm, such as infection, the stress of labour and caesarean section. -The woman should be seen monthly by the endocrinologist for clinical evaluation and monitoring of her thyroid levels. -Fetal well-being should also be monitored closely

Hypothyroidism: -Hypothyroidism occurs as the result of decreased activity of the thyroid gland - may lead to maternal and neonatal complications as well as being a cause of infertility. The most common cause of hypothyroidism in pregnancy is autoimmune thyroiditis (Hashimoto's disease). -It may also be induced following treatment for Graves' disease. -Slowing of the body's metabolic processes may occur giving rise to:

- mental and physical lethargy - excessive weight gain - constipation, cold intolerance and dryness of the skin. -Thyroid hormone is essential for human brain development results in impaired neurological development in childhood.

untreated hypothyroidism in pregnancy is associated with increased risk of: miscarriage pre-eclampsia fetal growth restriction placental abruption perinatal mortality and neonatal morbidity

-Women should be encouraged to increase their dietary iodine intake during pregnancy. -It is important to identify and treat hypothyroidism with daily thyroxin as early as possible in order to improve pregnancy outcome. - Following birth, thyroid status in the neonate should be checked to identify whether neonatal hypothyroidism is present.

-There is no contraindication to breastfeeding but the dose of thyroxin may need adjustment postpartum . Postpartum thyroiditis -an autoimmune disorder and is a form of Hashimoto's thyroiditis. - It occurs in 10% of women within 12 months following childbirth. -It is a transient thyroid disorder, characterized by a period of mild hyperthyroidism 1–4 months after the birth of her baby, followed by a phase of hypothyroidism

-In both phases the disorder presents with fatigue and a painless goiter. - the condition may also mimic postpartum depression. - Treatment is not required as recovery is usually spontaneous -the disorder tends to recur in subsequent pregnancies and may progress to permanent hypothyroidism .

Screening for thyroid disorders to reduce neonatal and child neurological development it is recommended by some authors that a screening programme for thyroid dysfunction should be undertaken in early pregnancy optimum iodine nutrition during pregnancy and identifying women with : (a) known thyroid disease (b) increased risk of thyroid disease, e.g. those with other autoimmune disorders. All babies are screened for congenital hypothyroidism as part of the newborn blood spot programme

Thank you