gebelikte hipotiroidi

 

Tedavi 

Halihazırda tiroid hormonu almayan hastalarda :  

Tedavi endikasyonları 

●TSH >4 mU/L

•Free T4 below the reference range, TPO antibodies positive or negative – All pregnant women with newly diagnosed, overt hypothyroidism (TSH above trimester-specific normal reference range [or above 4.0 mU/L if trimester-specific range unavailable]) with low free T4 should be treated with thyroid hormone 

•Free T4 within the reference range, TPO antibodies positive or negative – Because maternal euthyroidism is potentially important for normal fetal cognitive development, we and others [65] suggest treatment of pregnant women with newly diagnosed subclinical hypothyroidism (TSH above trimester-specific normal reference range [or above 4.0 mU/L if trimester-specific range unavailable], with normal free T4), regardless of thyroid peroxidase (TPO) antibody status (algorithm 1). The data assessing treatment with T4 in this subgroup of women are conflicting and limited by variability in the TSH criteria used to define hypothyroidism and the late initiation of thyroid hormone treatment (often late in the first trimester). 

This approach differs slightly from the ATA guidelines (reviewed at the end of this section), in which treatment recommendations are based on TPO antibody status [4].

●TSH 2.6 to 4 mU/L – For pregnant women with TSH in this range, we individualize the decision to treat based upon patient characteristics, values, and preferences. Some experts, including one editor of this topic, do not treat euthyroid pregnant women. Other experts, including the author and another editor of this topic, offer treatment to selected pregnant women based on the presence or absence of TPO antibodies, which have been associated with adverse pregnancy outcomes (eg, early pregnancy loss) 

•TPO antibodies positive – For pregnant women with a TSH between 2.6 mU/L and the upper limit of the trimester-specific reference range (or 4.0 mU/L if trimester-specific range unavailable), positive TPO antibodies, and a history of recurrent miscarriage, many experts (including the author and one editor of this topic) offer treatment with T4 (50 mcg daily) to those who prefer this intervention. This is based on weak evidence in view of conflicting data regarding the efficacy of T4 for reducing the risk of miscarriage. However, carefully monitored thyroid hormone treatment is safe. 

In the absence of a history of recurrent miscarriage, some experts (including one editor of this topic) also offer T4 (50 mcg daily) to those who prefer this intervention (based on weak evidence).

If a decision is made not to treat, TSH should be reassessed every four weeks during the first trimester and once each in the second and third trimester to monitor for the development of hypothyroidism. If TSH rises above the population and trimester-specific upper limit of normal (approximately 4 mU/L), we begin treatment with T4.

The management of women with TPO antibodies and normal thyroid function is reviewed in more detail elsewhere. 

•TPO antibodies negative – For pregnant women with a TSH between 2.6 mU/L and the upper limit of the trimester-specific reference range (or 4.0 mU/L if trimester-specific range unavailable), and negative TPO antibodies, we do not treat with T4.

For women at high risk for developing hypothyroidism (eg, history of radioiodine treatment, hemithyroidectomy, or exposure to high-dose irradiation of the head and neck), we monitor for the development of hypothyroidism by reassessing TSH approximately every four weeks during the first trimester and once during each of the second and third trimesters. If TSH rises above the population and trimester-specific upper limit of normal (approximately 4 mU/L), we begin treatment with T4.

●TSH between the trimester-specific lower limit of normal and 2.5 mU/L – These women are euthyroid and do not require T4 treatment.

●Low free T4, normal TSH (maternal hypothyroxinemia) – We do not typically treat pregnant women with isolated hypothyroxinemia (low free T4, normal TSH). 

The 2017 ATA guidelines base their treatment recommendations on TPO antibody status [4]. They recommend measurement of TPO antibodies in pregnant women with TSH >2.5 mU/L and treatment as follows:

●Positive TPO antibodies – Thyroid hormone should be considered if TSH is above 2.5 mU/L and should be initiated if TSH is above the population and trimester-specific upper limit of normal (approximately 4.0 mU/L).

●Negative TPO antibodies – Thyroid hormone should be considered if the TSH is above population and trimester-specific upper limit of normal but <10 mU/L and should be initiated if the TSH is >10 mU/L.

●Maternal hypothyroxinemia – The ATA does not suggest treatment of pregnant women with isolated hypothyroxinemia (low free T4, normal TSH).

Levothyroxine initial dosing — The treatment of choice for correction of hypothyroidism in pregnancy is the same as in nonpregnant patients: synthetic levothyroxine (T4). Several formulations of T4 are available. Because there may be subtle differences in bioavailability between T4 formulations, some endocrinologists feel that it is preferable to stay with the same formulation whenever possible. When using generic preparations, the manufacturer can be identified from the prescription label, and the patient may request refills from the same generic pharmaceutical company.

The goal of T4 replacement in pregnancy is to restore euthyroidism as soon as possible. General dosing guidance is as follows:

●TSH >4 mU/L (or above population and trimester-specific upper limit of normal), with low free T4 (using assay method and trimester-specific reference range) – Close to full replacement dose (approximately 1.6 mcg/kg body weight per day)

●TSH >4 mU/L, with normal free T4 – Intermediate dose (approximately 1 mcg/kg per day)

●TSH 2.6 to 4 mU/L – If a decision has been made to treat euthyroid women with TPO antibodies, low dose (typically 50 mcg daily)

T4 should be taken on an empty stomach, ideally an hour before breakfast, but few patients are able to wait a full hour.

Monitoring and dose adjustments — After initiation of T4 therapy, the patient should be reevaluated and serum TSH measured in four weeks.

The goal is to maintain TSH in the lower half of the trimester-specific reference range. If not available, a goal TSH of <2.5 mU/L is reasonable.

If the TSH remains above the normal trimester-specific reference range, the dose of T4 can be increased by 12 to 25 mcg/day. TSH should be measured every four weeks during the first half of pregnancy because dose adjustments are often required. TSH can be monitored less often (at least once each trimester) in the latter half of pregnancy, as long as the dose is unchanged.

Overtreatment should be avoided. Overtreatment with levothyroxine during pregnancy has been associated with an increase in preterm delivery (OR 2.14, 95% CI 1.51-2.78) [71]. In addition, one study suggested an association between overtreatment during pregnancy (free T4 >97th percentile with average TSH 0.05 to 0.08 mU/L) and behavioral difficulties in the children [72].

Postpregnancy adjustments — Since the criteria for treating pregnant women differ from the criteria from treating nonpregnant women, it is not always necessary to continue levothyroxine after delivery. In one study, 75 percent of women with subclinical hypothyroidism during pregnancy had normal thyroid function five years postpartum [73]. Because overt hypothyroidism may interfere with milk production, it may be prudent to delay assessment until the completion of breastfeeding. Unless another pregnancy is imminent, however, the majority of women who were started on levothyroxine for TSH between 2.5 and 4.0 mU/L do not need to continue levothyroxine treatment.