The thyroid is an endocrine gland located in front of the neck in humans. It is a butterfly-shaped gland with two lobes on either side and an isthmus(connecting area) in between.
Origins of the thyroid gland
The thyroid gland is the first amongst all endocrine glands to develop in an embryo. It starts developing in the 3rd week of gestation from the 1st/2nd endodermal pouches, near the base of the tongue. These cells form the thyroid follicles in a developed gland, responsible for thyroid hormones production.
There is another type of cells located around the follicles, known as the parafollicular cells or C-cells that produce Calcitonin, a hormone responsible for calcium homeostasis. C-cells develop around the 5th week from “ultimobranchial bodies” arising from the 4th/5th pharyngeal pouch and fuse with the thyroid gland as its descending from its original location near the base of the tongue to the final location lower central neck from 5th to 7th week of gestation.
By the 12th week, the thyroid gland is functionally ready. For the first trimester, the maternal hormone is responsible for fatal development and growth, however, by 16-18 weeks of gestation, the fetal thyroid gland can produce adequate amounts of fetal thyroid hormones to sustain the development.
Hypothyroidism in the first trimester of pregnancy, puts the baby at high risk for mental retardation.
Types of thyroid disorders
The thyroid is one of the most important glands in the body, its dysfunction can affect any system of the body. Thyroid disorders can primarily be divided into Benign (non-cancerous) and Malignant (cancers). Benign disorders can further be classified based on the functioning of the gland into the following:
- Hypothyroidism
- Hyperthyroidism
- Euthyroid disorders
First we will discuss symptoms of each in brief. Detailed discussion will follow in subsequent blogs.
Hypothyroidism
Hypothyroidism results from an under-functioning gland with low levels of circulating T3 & T4 hormones. Its signs and symptoms are listed below:
- Feeling tired & fatigued all the time
- Cold intolerance
- Chronic constipation
- Dry skin
- Weight gain
- Puffed up face
- Hoarseness in adults, hoarse cry in babies
- Muscle weakness
- High blood cholesterol level
- Muscle aches, tenderness and stiffness
- Pain, stiffness or swelling in your joints
- Heavier than normal or irregular menstrual periods
- Thinning hair
- Slowed heart rate – bradycardia
- Depression
- Impaired memory
- Enlarged thyroid gland (goitre)
- Jaundice in babies
- Macroglossia (large tongue) in babies
- Delayed milestones in babies
- Delayed puberty in teenagers
- Poor mental development
- Goitre
Hyperthyroidism
Hyperthyroidism is due to a hyper functioning gland. The signs and symptoms are listed below:
- Unintended weight loss, despite a normal or increased appetite.
- Rapid heartbeat (tachycardia – more than 100 beats a minute)
- Irregular heartbeat (arrhythmia)
- Palpitations
- Increased appetite
- Nervousness, anxiety and irritability
- Tremors in hands and fingers
- Excessive sweating
- Changes in menstruation
- Heat intolerance
- Frequent bowel movements
- Goitre – a swelling at the base of your neck
- Fatigue, muscle weakness
- Disturbed sleep
- Skin thinning
- Fine, brittle hair
Euthyroid disorders
In these patients the gland function is normal, but the patient presents with a swelling in the neck such as euthyroid goitre, solitary nodule in the gland, thyroglossal cyst, ectopic gland, lingual thyroid etc.
Consult with Dr Akanksha Saxena, ENT & Head & Neck Surgeon for any related problems.
