The results of the present study demonstrate that sexual dimorphism in the rat thyroid is due to a difference in the average volume of thyroid follicular cells. Goiter is a condition in which the thyroid gland enlarges, either as a whole or with one or more small lumps called thyroid nodules. The thyroid is an essential organ of the endocrine system, located in the front of the neck, just above where the collarbones meet. It produces hormones that control how each cell in the body uses energy.
During embryonic development, it remains connected to the tongue by a narrow channel, known as the thyroglossal duct. If you don't have enough iodine in your diet, your thyroid will enlarge to try and capture as much iodine as possible, so it can produce the right amount of thyroid hormone. Abnormalities during prenatal development can lead to various forms of thyroid dysgenesis, which can cause congenital hypothyroidism and, if left untreated, can result in cretinism. Psychological symptoms may also accompany thyroid disorders and there are various treatment and management options available. In addition to hormones that control energy use, the thyroid also produces calcitonin, a hormone that helps regulate calcium levels in the blood. Thyroid disorders include hyperthyroidism, hypothyroidism, inflammation of the thyroid (thyroiditis), enlarged thyroid (goiter), thyroid nodules, and thyroid cancer.
In most tetrapod species, there are two paired thyroid glands - right and left lobes that are not joined. The thyroid is situated near the front of the neck and is located against and around the front of the larynx and trachea. This study was designed to determine whether sex-dependent differences in thyroid gland structure in adult male and female rats depend on quantitative or qualitative changes in thyroid follicular cells. Arterial blood is supplied to the thyroid from two sources: the superior thyroid artery (a branch of the external carotid artery) and the lower thyroid artery (a branch of the thyrocervical trunk). An anatomical variant known as the imthyroid artery may also be present; its origin varies. Chronic thyroiditis (Hashimoto's disease) is a persistent inflammation of the thyroid that develops slowly and often leads to hypothyroidism - a decreased function of the gland. Goiter can be a general enlargement of the thyroid or it can be caused by irregular cell growth that forms one or more lumps (nodules) in the gland.
Most goiters are painless; however, if you have thyroiditis (inflammation of the gland), it can be painful. During embryo development at 3-4 weeks of gestational age, the thyroid appears as an epithelial proliferation in the pharyngeal floor at the base of the tongue between the odd tubercle and copula linguae. The effects of calcitonin are opposite to those of parathyroid hormone (PTH) produced by parathyroid glands.