Thyroid Disorders

Thyroid Disorders Overview

  • Presenter: Matthew Heppel-Holden, an Advanced Diabetes and Endocrinology Pharmacist at Hull University Teaching Hospitals, UK.

  • Event: Clinical Pharmacy Association Diabetes and Endocrinology Committee session on thyroid disorders.

Session Objectives

By the end of this session, participants should be able to:

  • Provide an overview of the pathology and aetiology of various thyroid disorders.

  • Outline how thyroid hormones are produced.

  • Interpret common thyroid function tests related to thyroid gland disorders.

  • Formulate treatment management plans based on national guideline recommendations for hypothyroidism and hyperthyroidism.

  • Understand severe complications arising from untreated or uncontrolled hypothyroidism and thyrotoxicosis.

Thyroid Anatomy

  • Thyroid Gland Structure:

    • Right lobe, left lobe, pyramidal lobe, isthmus, and associated structures like the cricoid and thyroid cartilage.

    • Related Structures: Hyoid bone, cricothyroid ligament, and trachea.

Functions of the Thyroid

  1. Synthesis of Thyroid Hormones:

    • Produces T3 (triiodothyronine) and T4 (thyroxine), which impact:

      • Cardiovascular function

      • Metabolism

      • Development

      • Other systemic functions

  2. Secretion of Calcitonin:

    • Helps maintain serum calcium and phosphate levels via parathyroid hormone (PTH) secretion from parathyroid glands.

Synthesis and Role of Thyroid Hormones

  • T4 to T3 Conversion:

    • The conversion ratio is approximately 10:1; T4 is the inactive prohormone, while rT3 is the inactive metabolite of T4.

    • T4 is highly protein-bound.

Thyroid Disorders

  • Types of Hypothyroidism:

    • Primary Hypothyroidism:

      • Overt and subclinical forms.

    • Secondary Hypothyroidism: Caused by pituitary or hypothalamic dysfunction.

    • Peripheral Hypothyroidism:

      • Results from peripheral resistance to thyroid hormones.

  • Types of Hyperthyroidism:

    • Thyroidal origin, pituitary disease, and extrathyroidal origins.

Signs and Symptoms of Hypothyroidism

Common Symptoms:

  • Brain fog and memory issues.

  • Mental health issues, including depression.

  • Physical manifestations:

    • Thinning hair and eyebrow loss.

    • Goiter formation (enlarged thyroid).

    • Jaundice in affected infants.

    • High blood pressure and heart attack risks.

    • Slowed metabolism, leading to weight gain, constipation, and gastrointestinal issues.

    • Menstrual changes in women, dry skin, and muscle weakness.

General Symptoms of Primary Hypothyroidism:

  • Fatigue, hoarse voice, bradycardia, pericardial effusion, and diastolic hypertension.

  • Signs such as facial swelling (particularly eyelids), brittle nails, coarse hair, and reduced sweating, among others.

Causes of Hypothyroidism:

  • Can result from autoimmune thyroiditis (e.g., Hashimoto's thyroiditis), iodine deficiency, post-surgical effects or radioactive iodine treatment, and congenital diseases.

Diagnosis of Hypothyroidism

Steps:

  1. Assess symptoms.

  2. Conduct biochemical testing: Thyroid Function Tests (TFTs) focusing on TSH and free T4 levels.

Interpreting Thyroid Function Tests:

  • Raised TSH and low FT4 suggest overt primary hypothyroidism.

  • Slightly raised TSH with normal FT4 indicates subclinical primary hypothyroidism.

  • Low TSH and FT4 imply secondary hypothyroidism.

Additional Investigations:

  • Thyroid antibodies testing for Thyroid PerOxidase Antibodies (TPOAb), Thyroglobulin Antibodies (TgAb), and TSH receptor antibodies (TRAb).

  • Glucocorticoid deficiency testing using the Short Synacthen Test.

Treatment of Hypothyroidism

Aims of Treatment:

  1. Effectively replace thyroid hormone.

  2. Correct TSH levels and resolve clinical symptoms.

Treatment Plan:

  • First-line therapy: Levothyroxine (T4) replacement, with a typical starting dose of 1.6 micrograms per kg, adjusted accordingly for older patients or those with pre-existing conditions.

  • Monitoring: TFTs every 3 months until stable, then annually.

Levothyroxine Counseling Points:

  • Importance of compliance, timing of administration, and interactions with food and drugs.

  • Guidance on the significance of monitoring requirements, especially during pregnancy and breastfeeding.

Myxoedema Crisis

  • Describes a severe manifestation of hypothyroidism characterized by symptoms like hypothermia and periorbital swelling, often precipitated by stress or infection.

Treatment of Myxoedema Crisis:

  • Requires IV treatment and symptomatic management.

Overview of Hyperthyroidism

Signs and Symptoms of Hyperthyroidism:

  • Bulging eyes (Graves’ disease), brittle hair, and an enlarged thyroid (goiter).

  • Symptoms include insomnia, anxiety, palpitations, weight loss despite increased appetite, nausea, and changes in menstrual cycles.

Types of Hyperthyroidism:

  • Graves' disease, nodular disease, thyroiditis, and pituitary disease.

Diagnosis of Hyperthyroidism

Underlying Causes:

  1. Symptoms assessment.

  2. Biochemical testing, including TSH, Free T4, and Free T3.

Treatment Approaches:

  • Aim to manage acute symptoms and maintain a euthyroid state.

  • Options include antithyroid drugs (thionamides), radioactive iodine, and thyroidectomy depending on the patient's condition and preferences.