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Hypothyroidism

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Introduction

Hypothyroidism is a condition in which a person's thyroid hormone production is below normal. Common causes of the disease is chronic autoimmune thyroiditis, post surgery and post radio active iodine.
Thyroid disorders are conditions that affect the thyroid gland. There are specific kinds of thyroid disorders that includes hypothyroidism, hyperthyroidism, goiter, thyroid nodules and thyroid cancer.

Risk Factors

Signs and symptoms

Diagnostic criteria

The symptoms depend on the deficiency of thyroid hormone, but can include:

• Increased cholesterol levels
• Depression
• Fatigue
• Hair loss
• Memory loss
• Dry, rough skin
• Constipation
• Hoarse voice

Investigations

A blood test is used to confirm hypothyroidism

Management

Monitoring

• TSH monitoring 6–8 weeks after any levothyroxine dose change, and yearly life– long monitoring once euthyroidism is achieved (target TSH 0.2–4.0 um/l). FT4 can be measured in early stages of treatment.
• In patients with central hypothyroidism, assessments of serum free T4 should guide therapy and targeted to exceed the mid normal range value for the assay being used.
• Wait for TSH equilibration–TSH equilibration requires eight to 12 weeks after any thyroxine dosage change. Once a stable dose is achieved–yearly TSH is sufficient.

In Pregnancy

When the elevation of the TSH level is confirmed, free T4 should be measured in order to classify the hypothyroidism as clinical or overt (OH) and subclinical (SH).

• TSH > 2.5–10.0 mU/L with normal free T4: SH.
• TSH > 2.5 –10.0 mU/L with low levels of free T4: OH.
• TSH =10.0 mU/L, despite the level of free T4: OH

Women in reproductive period should be euthyroid before conceiving, as the hypothyroidism is associated with neural development. Dose may be doubled during pregnancy and returned to normal dose after delivery.

  • Non-pharmacological

    Indications for Treatment

    • TSH level persistently > 10 mU/L; treat all patients due to, increased likelihood of progression to overt disease and a higher risk of congestive heart failure, cardiovascular disease and mortality.
    • TSH levels (4.5–10 mU/L); consider, treatment in patients younger than 65 with increased cardiovascular risk (e.g., previous cardiovascular disease, hypertension, documented diastolic dysfunction, atherosclerotic risk factors (dyslipidaemia, diabetes mellitus, smoker), goitre, positive antithyroid peroxidase antibodies, evidence of autoimmune thyroiditis by ultrasound, pregnancy, or infertility), particularly when TSH level is persistently > 7 mU/L.
    • Levothyroxine therapy could be considered also for symptomatic middle-aged patients for a short period of time. If a clear beneficial effect is observed, levothyroxine therapy could be maintained.
    • Persistently mildly increased TSH levels (>4.5–10 mU/L) with positive Thyroid Antibody and thyroid sonographic findings typical of autoimmune thyroiditis.
  • Pharmacological

    Initial dose:
    • Clinical hypothyroidism–Levothyroxine 1.6–1.8 µg/kg ideal body weight Subclinical hypothyroidism–Levothyroxine 1.1–1.2 µg/kg is recommended
    • Take at least after 2 hours fast, 30 minutes before food intake. Alternatively at bedtime (3 or more hours after the evening meal).
    • When initiating therapy in young healthy adults with overt hypothyroidism, consider beginning treatment with full replacement doses
    • Routine use of combined therapy with levothyroxine and triiodothyronine for hypothyroid patients is not recommended
    • Assess TSH and adjust dosage when there are large changes in body weight, with aging, and with pregnancy.
    • There is no convincing evidence to support routine use of thyroid extracts, L-T3 monotherapy, compounded thyroid hormones, iodine containing preparations, dietary supplementation, and over the counter preparations in the management of hypothyroidism.

Prevention

Updated on,

25 Novemba 2020 12:18:13

References

1. STG

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