Thyroid gland

• Hypothalamus-pituitary complex

  Brain's central command center to control vital bodily functions

  
• Hypothalamus

  • Part of the brain that's in charge of some of the body's basic operations
  • Sends messages to the autonomic nervous system
  • Tells the pituitary gland to produce and release hormones that affect other areas of the body

  
• Pituitary gland

  • Connected to hypothalamus through a stalk of blood vessels and nerves
  • Communicates with the anterior pituitary lobe via hormones and the posterior lobe through nerve impulses
  • Creates oxytocin and antidiuretic hormone and tells posterior pituitary when to store and release

  
• Hypothalamus-releasing hormones

  • Growth hormone releasing hormone (GHRH)
  • Gonadotropin-releasing hormone (GnRH)
  • Corticotropin-releasing hormone (CRH)
  • Thyrotropin-releasing hormone (TRH)
  • Dopamine (inhibition)
• Hormones released by the anterior pituitary in response

  • Growth hormone (GH)
  • Follicle-stimulating hormone (FSH) and luteinizing hormone (LH)
  • Adrenocorticotropic hormone(ACTH)
  • Thyroid-stimulating hormone (TSH)
  • Prolactin (PRL)

  
• Effects of the hormones

  Growth hormone stimulates growth

  FSH and LH control the menstrual cycle and trigger ovulation

  ACTH stimulates the adrenal glands to produce cortisol

  TSH stimulates the thyroid gland to produce thyroid hormones

  Prolactin stimulates breast milk production

  
• Posterior pituitary lobe

  • Stores and releases antidiuretic hormone (ADH) and oxytocin

  
• Anterior pituitary lobe

  • Makes and releases adrenocorticotropic hormone (ACTH), thyroid-stimulating hormone (TSH), follicle-stimulating hormone (FSH), luteinizing hormone (LH), growth hormone (GH), and prolactin

  
• Thyroid gland


  Controls the speed of metabolism
• Thyroid-stimulating hormone (TSH)


  Stimulates the thyroid to produce thyroid hormones that manage metabolism, energy levels and the nervous system

  
• Hypothalamus - pituitary - thyroid axis

  Neurons in the hypothalamus release TRH, which stimulates the anterior pituitary to secrete TSH, which in turn stimulates the thyroid to release T3 and T4

  High levels of T3/T4 decrease TSH secretion, low levels increase TSH release

  
• Thyroid dysfunction

  • Second most common glandular disorder of the endocrine system

  Increasing, predominantly among women

  Undetected cases may be twice as many as detected

  
• Hypothyroidism

  Decrease in thyroid hormone production and thyroid gland function

  Caused by chronic thyroiditis, radioactive iodine, surgery, and certain medications

  Leads to symptoms like constipation, weight gain, lethargy, intolerance to cold, dry and cool skin, puffiness of the face and eyelids, and slow heart rate

  
• Oral manifestations of hypothyroidism

  • Thick lips, large protruding tongue (macroglossia), malocclusion, delayed eruption of teeth, impaction of mandibular second molars
• Common oral findings in hypothyroidism

  • Macroglossia, dysgeusia, delayed eruption, poor periodontal health, altered tooth morphology, delayed wound healing
• Hyperthyroidism

  Thyrotoxicosis, more common in women and smokers

  Symptoms include heat intolerance, palpitations, anxiety, fatigue, weight loss, muscle weakness, irregular menses

  Clinical findings include tremor, tachycardia, lid lag, warm moist skin
• Oral manifestations of hyperthyroidism

  • Increased susceptibility to caries, periodontal disease, enlargement of extraglandular thyroid tissue, maxillary or mandibular osteoporosis, accelerated dental eruption, burning mouth syndrome

  
• Primary vs secondary thyroid disorders

  In primary, the thyroid produces excessive or insufficient T3/T4, suppressing or increasing TSH

  In secondary, the pituitary produces excessive or insufficient TSH, stimulating or failing to stimulate the thyroid

  
• Thyroid function tests

  • TSH, T3, T4

  
• TSH is the first-line screening test for suspected thyroid problems

  
• Primary hypothyroidism

  Insufficient amounts of T3 and T4, which leads to loss of negative feedback inhibition, and increased production of TSH from the anterior pituitary

  
• Secondary hyperthyroidism

  The anterior pituitary produces large amounts of TSH, which, in turn, stimulate the thyroid follicular cells to secrete thyroid hormones in excessive amounts

  
• Secondary hypothyroidism


  The anterior pituitary produces low levels of TSH, lack of stimulation of thyroid follicular cells causes T3 and T4 levels to go down

  
• Thyroid function tests

  1. Measure the levels of T3, T4, and TSH in the blood

  2. Critical for diagnosing thyroid problems

  3. Differentiate between a primary and a secondary cause of thyroid disease

  
• Change in TSH that parallels T3 and T4 changes


  Indicates a secondary problem originating in the anterior pituitary
• TSH change that follows the opposite direction of T3 and T4


  Suggests a problem in the thyroid gland itself

  
• Role of endocrinologist


  • Physicians who treat children and adults with thyroid disorders
  • Opportunity to expand a dentist's referral base
  • Regular communication with dentist is critical for safe and optimal treatment of thyroid patients

  
• Role of dentist


  • May be the first to suspect a serious thyroid disorder and aid in early diagnosis
  • Avoid possible dental complications resulting from treating patients with thyroid disorders
  • Modifications of dental care must be considered when treating patients with thyroid disease

  
• Protecting the thyroid gland

  Use a thyroid collar while taking patient X-rays

  
• Treating patients with thyroid disease

  • Awareness of the condition and current stage of treatment is important
  • Length and current state of therapy are important in understanding the metabolic control of patients
  • Consultation with the patient's primary care physician or an endocrinologist is warranted if any sign or symptom of thyroid disease is noted on examination

  
• Responsibilities of oral health care provider

  • Stress reduction
  • Awareness of drug side effects or interactions
  • Vigilance for appearance of signs or symptoms of hormone toxicity
• Many signs and symptoms of thyroid disease are observable during examination of the orofacial complex

  
• Under or over activity of the thyroid gland can cause life-threatening cardiac events
• Dental treatment modification may be necessary for dental patients under medical management and follow-up for a thyroid condition
• If a suspicion of thyroid disease arises for an undiagnosed patient, all elective dental treatment should be postponed until a complete medical evaluation is performed
• A medically well-controlled patient will have no contraindications to have dental treatment
• Dental management of hypothyroidism

  • Increased subcutaneous mucopolysaccharides may decrease the ability of small blood vessels to constrict when cut and may result in increased bleeding
  • Delayed wound healing may be associated with an increased risk for infection
  • Susceptibility to cardiovascular disease from arteriosclerosis and elevated LDL
  • Sensitive to central nervous system depressants and barbiturates

  
• Recent exposure to a surgical antiseptic that includes iodine can increase the risk of thyroiditis or hypothyroidism
• Drug interactions of l-thyroxine

  • Increased metabolism due to phenytoin, rifampicin and carbamazepine
  • Impaired absorption with iron sulfate, sucralfate and aluminum hydroxide
  • Increases the effects of warfarin sodium
  • Elevates l-thyroxine levels with concomitant use of tricyclic antidepressants
• Dental management of hyperthyroidism


  • Elevated blood pressure and heart rate
  • Increased metabolism of warfarin sodium
  • Anti-thyroid drugs like propylthiouracil (PTU) have anti-vitamin K activity and can cause hypoprothrombinemia and bleeding
  • Combination analgesics containing acetylsalicylic acid (ASA) are contraindicated
  • NSAIDs should be used with caution
  • Epinephrine is contraindicated, and elective dental care should be deferred for patients exhibiting signs or symptoms of thyrotoxicosis