101
Sub-Acute Thyroiditis
It is associated with increased secretion of stored thyroid hormones as a consequence of viral infection of thyroid glands, also known as spontaneously resolving
thyrotoxicosis [2].
Thyroid Neoplasms
Thyroid neoplasm is a neoplasm or tumour of the thyroid. It can be a benign tumour
such as thyroid adenoma, or it can be a malignant neoplasm (thyroid cancer), such
as papillary, follicular, medullary or anaplastic thyroid cancer [2].
Metabolic Abnormalities and Thyroid Functions
Alterations in normal regulation mechanisms of body in certain metabolic disorders
result in impaired thyroid function. On the other hand, thyroid dysfunction may
interfere with normal metabolic processes of the body, leading to metabolic abnormalities. In this chapter, we will discuss both the causes and consequences of
impaired thyroid functions in relation to metabolic disorders.
Thyroid Hormones and Obesity
A bidirectional association exists between obesity and thyroid hormones, with
influence of obesity on thyroid function and hypothyroidism affecting body mass
index (BMI) and body weight. The anomalies of thyroid functions are frequently
observed in obese individuals [12].
The leptin is a 16 kilo-dalton hormone released from adipose tissues and acts on
arcuate neurons of hypothalamus. The role of leptin signalling on the maintenance
of hypothalamic TRH expression has recently been reported. The leptin hormone
controls the thyroid function via acting directly on leptin receptors present in TRH
neurons, or through projections of arcuate neuron in TRH neurons. Increased level
of adipocytes in obese individuals results in increased release of leptin which consequently stimulates the secretion of TRH and TSH via JAK-2/STAT-3 pathway,
leading to hypothyroidism (Fig. 6.2) [13].
A positive correlation has been observed between body mass index, body weight
and thyrotropin (TSH) in obese individuals although thyroid function seems to be
normal [14]. Many studies in different age groups have shown an elevation in the
level of TSH in obesity. Slight elevations in the serum TSH level along with normal
thyroid functions among obese subjects can be characterised as subclinical
hyperthyroidism. Among the causes of increased TSH levels in obesity, iodine
6 Impaired Thyroid Function in Metabolic Disorders
Sub-Acute Thyroiditis
It is associated with increased secretion of stored thyroid hormones as a consequence of viral infection of thyroid glands, also known as spontaneously resolving
thyrotoxicosis [2].
Thyroid Neoplasms
Thyroid neoplasm is a neoplasm or tumour of the thyroid. It can be a benign tumour
such as thyroid adenoma, or it can be a malignant neoplasm (thyroid cancer), such
as papillary, follicular, medullary or anaplastic thyroid cancer [2].
Metabolic Abnormalities and Thyroid Functions
Alterations in normal regulation mechanisms of body in certain metabolic disorders
result in impaired thyroid function. On the other hand, thyroid dysfunction may
interfere with normal metabolic processes of the body, leading to metabolic abnormalities. In this chapter, we will discuss both the causes and consequences of
impaired thyroid functions in relation to metabolic disorders.
Thyroid Hormones and Obesity
A bidirectional association exists between obesity and thyroid hormones, with
influence of obesity on thyroid function and hypothyroidism affecting body mass
index (BMI) and body weight. The anomalies of thyroid functions are frequently
observed in obese individuals [12].
The leptin is a 16 kilo-dalton hormone released from adipose tissues and acts on
arcuate neurons of hypothalamus. The role of leptin signalling on the maintenance
of hypothalamic TRH expression has recently been reported. The leptin hormone
controls the thyroid function via acting directly on leptin receptors present in TRH
neurons, or through projections of arcuate neuron in TRH neurons. Increased level
of adipocytes in obese individuals results in increased release of leptin which consequently stimulates the secretion of TRH and TSH via JAK-2/STAT-3 pathway,
leading to hypothyroidism (Fig. 6.2) [13].
A positive correlation has been observed between body mass index, body weight
and thyrotropin (TSH) in obese individuals although thyroid function seems to be
normal [14]. Many studies in different age groups have shown an elevation in the
level of TSH in obesity. Slight elevations in the serum TSH level along with normal
thyroid functions among obese subjects can be characterised as subclinical
hyperthyroidism. Among the causes of increased TSH levels in obesity, iodine
6 Impaired Thyroid Function in Metabolic Disorders