Key Topics

• • Introduction to endocrine disorders
• • Pituitary disorders, growth hormone and acromegaly
• • Thyroid disorders, their impact on oral health and patient management
• • Corticosteroids – their role in the stress response, as well as modulating immune and inflammatory responses
• • Pregnancy and dental care

Learning Objectives

• • Be aware that dental clinicians may be well placed to detect undiagnosed endocrine conditions, such as acromegaly
• • Be aware of the impact of thyroid disorders on oral health, and potential issues, such as a thyroid storm
• • Be aware that reduced corticosteroid levels may impact upon a patient’s ability to cope with stress, whilst chronic, high levels may lead to immune suppression
• • Be aware that routine dental therapy is not only safe during pregnancy, but may improve health outcomes for both mother and newborn
• • Be aware that declining levels of oestrogen and progesterone associated with the menopause may have a negative impact upon oral health

Introduction

The endocrine system works together with the nervous system to control many aspects of body function. As a generalization, the endocrine system is responsible for more widespread, longer-term control within our body. However, there is significant communication and coordination between the nervous and endocrine systems, particularly through the hypothalamic-pituitary axis. The pituitary gland itself is commonly viewed as the ‘master’ gland of the endocrine system, since its endocrine secretions not only have direct influences in the body, but also regulate the activity of other endocrine glands. However, much of the secretory activity of the pituitary gland is controlled by the hypothalamus.

In terms of both dental and medical practice, the endocrine disorder that has the most significant and widespread impact is diabetes mellitus. Because of its significant implications on oral health and the management of patients within the dental clinic, we shall discus diabetes mellitus in a separate chapter. In this chapter we will examine the other endocrine conditions, and the clinical use of exogenous hormones, that may impact upon oral health and the management of dental patients.

Disorders of endocrine function, as well as the use of exogenous hormones, can have widespread impacts on the body, and may affect:

• Growth and development
• Energy metabolism
• Muscle and adipose tissue distribution
• Sexual development
• Fluid and electrolyte balance
• Inflammation and immune responses.

Obviously, a number of these factors may impact upon oral health and patient wellbeing. Endocrine disturbances are normally associated with either hypo- or hyperfunction of the endocrine glands. Disorders may be directly associated with a defect in the endocrine gland responsible for producing a particular hormone (primary disorder). Conversely, a particular endocrine gland may be fully functional, but its’ activity may be affected by defective levels of a particular stimulating hormone or releasing factor. This is referred to as a secondary disorder, and is commonly associated with altered pituitary function. Finally, hypothalamic dysfunction may impact upon pituitary gland function, giving rise to a tertiary disorder.

In terms of this chapter, we will focus on the endocrine disorders, or hormones that may impact upon the dental patient and their oral health.

Pituitary gland

The pituitary gland releases eight major hormones. Six of these, growth hormone, adrenocorticotropin, thyroid-stimulating hormone, prolactin, follicle-stimulating hormone and luteinizing hormone are released by the anterior pituitary, and two, antidiuretic hormone (or vasopressin) and oxytocin, are released by the posterior pituitary. For those hormones that influence the activity of other endocrine glands, we will consider their impacts on oral health separately. In terms of those hormones with direct actions, oral health implications are observed with altered levels of growth hormone, and potentially antidiuretic hormone.

Growth hormone, as the name suggests is important for normal growth and development, but it also has impacts on metabolism, promoting lean body mass and the use of fatty acids as an energy source. In children, the effects of a deficiency in growth hormone, or its activity, will impact upon normal development, and may lead to short stature (pituitary dwarfism). There are impacts in the oral cavity, particularly with mandibular, but also maxillary growth. Normal development of the roots and supporting structures of the teeth is retarded, and malocclusion may be associated with the smaller dental arches. There are also delays in both the normal eruption and shedding of teeth. In adults, the impacts of growth hormone deficiency are more associated with metabolic disturbances, although reduced bone mineral density may be observed. In both children and adults, management is primarily associated with growth hormone replacement therapy, although for children with defective growth hormone receptors, the developmental issues can be managed with the use of insulin-like growth factor 1.

There are also problems associated with excessive growth hormone production. In children, an excess of growth hormone can lead to gigantism associated with increased linear bone growth. Oral and dental development is normally in proportion to the body overall. There is a somewhat different picture associated with growth hormone excess that occurs during the adult years, giving rise to a condition known as acromegaly. Most commonly the condition occurs as a result of neoplasia of the growth hormone secreting cells in the pituitary. After the epiphyseal plates fuse, there can be no increase in stature. Instead, the condition is characterized by disproportionate growth mainly affecting the face, extremities such as the hands, and internal organs. The craniofacial changes tend to be characteristic of the disease, and the onset may be insidious. As such, dental professionals may be best placed to detect some of the early changes. Some of the more obvious oral signs include mandibular prognathism and thickening, increased thickening and height of the alveolar process, the spacing and flaring of anterior teeth, associated malocclusion, and an enlarged tongue. The metabolic implications of growth hormone excess may lead to diabetes mellitus. Management may involve drugs that inhibit growth hormone release, such as the dopamine agonist, bromocriptine, or the somatostatin analogue, octeotide. Stereotactic radiosurgery may also be an option.

Antidiuretic hormone (ADH), or vasopressin, plays an important role in regulating water balance in the body, facilitating the production of a concentrated urine by the kidneys by increasing the water permeability of the collecting ducts, promoting water reabsorption. A deficiency in ADH secretion, or action, leads to a condition known as diabetes insipidus. Like diabetes mellitus, polyuria is a key symptom, but in this case it is associated with the production of large volumes of a dilute urine. These effects may be exacerbated by some medications, such as NSAIDs, which reduce vasopressin’s effects. The potential for xerostomia is likely to be the main oral issue. Therapeutic management may involve the vasopressin analogue, desmopressin.

Thyroid gland

Disorders of the thyroid gland are the second most common form of endocrine disease after diabetes mellitus, and a number of these disorders have an autoimmune basis. The thyroid gland plays a very important role in regulating metabolism, but also influences normal growth and development, including tooth eruption. There are three key hormones produced by the thyroid gland, thyroxin (T4) and tri-iodothyronine (T3), commonly referred to as the thyroid hormones, and also calcitonin. The production of T4 and T3 is regulated by the pituitary hormone, thyroid-stimulating hormone (TSH).

Hyperthyroidism

Hyperthyroidism, or thyrotoxicosis, is associated with excessive thyroid hormone secretion leading to a high metabolic rate, and a variety of associated symptoms, including increased skin temperature and sweating, weight loss, nervousness and tachycardia. Patients with hyperthyroidism are prone to cardiovascular disease, including arrhythmias, due to the effects of the hormone on the heart. The two common forms of hyperthyroidism are toxic nodular goitre and diffuse toxic goitre (Grave’s disease). Toxic nodular goitre is associated with benign neoplasia, while diffuse toxic goitre has an autoimmune basis, with autoantibodies activating the TSH receptors. This condition is also associated with an increased sensitivity to catecholamines, and the problem of exophthalmos, caused by excessive connective tissue deposition in the orbits.

Hyperthyroidism can be treated surgically, but is more commonly managed by drugs that reduce thyroid hormone production, although these do not address the underlying autoimmune problem. Radioactive iodine (¹³¹I) can exert very selective cytotoxic effects on the thyroid follicle cells, while thioureylenes, such as carbimazole, will decrease thyroid hormone synthesis. Beta-adrenergic antagonists may be used for symptomatic control of the problems such as tachycardia and muscle tremors. Corticosteroids, such as prednisolone have been used to manage the exophthalmos, although there is currently an interest in using other disease-modifying immunosuppressant drugs.

In terms of the dental implications, patients with hyperthyroidism are more susceptible to caries and periodontal disease, and may be prone to other oral problems, such as burning mouth syndrome. For patients with existing hyperthyroidism, it is important to assess