Toxic multinodular goiter (TMNG), also known as multinodular toxic goiter (MNTG), is an active multinodular goiter associated with

hyperthyroidism Hyperthyroidism is the condition that occurs due to excessive production of thyroid hormones by the thyroid gland. Thyrotoxicosis is the condition that occurs due to excessive thyroid hormone of any cause and therefore includes hyperthyroidis ...

. It is a common cause of hyperthyroidism in which there is excess production of

thyroid hormones File:Thyroid_system.svg, upright=1.5, The thyroid system of the thyroid hormones T3 and T4 rect 376 268 820 433 Thyroid-stimulating hormone rect 411 200 849 266 Thyrotropin-releasing hormone rect 297 168 502 200 Hypothalamus rect 66 216 386 ...

from functionally autonomous

thyroid nodule Thyroid nodules are nodules (raised areas of tissue or fluid) which commonly arise within an otherwise normal thyroid gland. They may be hyperplastic or tumorous, but only a small percentage of thyroid tumors are malignant. Small, asymptomatic ...

s, which do not require stimulation from thyroid stimulating hormone (TSH). Toxic multinodular goiter is the second most common cause of hyperthyroidism (after

Graves' disease Graves' disease (german: Morbus Basedow), also known as toxic diffuse goiter, is an autoimmune disease that affects the thyroid. It frequently results in and is the most common cause of hyperthyroidism. It also often results in an enlarged thyro ...

) in the developed world, whereas iodine deficiency is the most common cause of

hypothyroidism Hypothyroidism (also called ''underactive thyroid'', ''low thyroid'' or ''hypothyreosis'') is a disorder of the endocrine system in which the thyroid gland does not produce enough thyroid hormone. It can cause a number of symptoms, such as ...

in developing-world countries where the population is iodine-deficient. (Decreased iodine leads to decreased thyroid hormone.) However, iodine deficiency can cause goiter (thyroid enlargement); within a goitre, nodules can develop. Risk factors for toxic multinodular goiter include individuals over 60 years of age and being female.

Signs and symptoms

Symptoms of toxic multinodular goitre are similar to that of

, including: *

heat intolerance Heat intolerance is a symptom characterized by feeling ''overheated'' in ''warm'' environments or when the surrounding environment's temperature rises. Typically, the person feels uncomfortably hot and sweats excessively. Compared to heat ill ...

* muscle weakness/wasting * hyperactivity *

fatigue Fatigue describes a state of tiredness that does not resolve with rest or sleep. In general usage, fatigue is synonymous with extreme tiredness or exhaustion that normally follows prolonged physical or mental activity. When it does not resolve ...

* tremor * irritability *

weight loss Weight loss, in the context of medicine, health, or physical fitness, refers to a reduction of the total body mass, by a mean loss of fluid, body fat ( adipose tissue), or lean mass (namely bone mineral deposits, muscle, tendon, and other co ...

osteoporosis Osteoporosis is a systemic skeletal disorder characterized by low bone mass, micro-architectural deterioration of bone tissue leading to bone fragility, and consequent increase in fracture risk. It is the most common reason for a broken bone a ...

* increased appetite * non-painful goitre (swelling of the thyroid gland) *

tachycardia Tachycardia, also called tachyarrhythmia, is a heart rate that exceeds the normal resting rate. In general, a resting heart rate over 100 beats per minute is accepted as tachycardia in adults. Heart rates above the resting rate may be normal ( ...

(high heart rate - above 100 beats per minute at rest in adults) * tracheal compression * exophthalmos

Causes

Sequence of events: # Iodine deficiency leading to decreased T4 production. # Induction of thyroid cell hyperplasia due to low levels of T4. This accounts for the multinodular goitre appearance. # Increased replication predisposes to a risk of mutation in the TSH receptor. # If the mutated TSH receptor is constitutively active, it would then become 'toxic' and produces excess T3/T4 leading to hyperthyroidism.

Diagnosis

Treatments

Toxic multinodular goiter can be treated with antithyroid medications such as

propylthiouracil Propylthiouracil (PTU) is a medication used to treat hyperthyroidism. This includes hyperthyroidism due to Graves' disease and toxic multinodular goiter. In a thyrotoxic crisis it is generally more effective than methimazole. Otherwise it is ...

or methimazole, radioactive iodine, or with surgery. Another treatment option is injection of ethanol into the nodules.

History

The

usage The usage of a language is the ways in which its written and spoken variations are routinely employed by its speakers; that is, it refers to "the collective habits of a language's native speakers", as opposed to idealized models of how a languag ...

of terminology for types of goiter has varied over the past century. Physicians and surgeons tend to differentiate among solitary-nodule goiter, multinodular goiter, and non-nodular goiter more thoroughly in recent decades than they formerly did. Thus some sources have described, or still describe,

thyroid adenoma A thyroid adenoma is a benign tumor of the thyroid gland, that may be inactive or active (functioning autonomously) as a toxic adenoma. Signs and symptoms A thyroid adenoma may be clinically silent ("cold" adenoma), or it may be a functional tumo ...

(toxic adenoma) as

synonym A synonym is a word, morpheme, or phrase that means exactly or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are al ...

ous with toxic multinodular goiter, but other sources differentiate those two as single-nodule disease versus multinodular disease (respectively) with pathogenesis that is likely differing in most cases (e.g., single neoplastic cell clone versus multifocal or diffuse molecular metabolic change). The medical eponyms "Plummer disease" (named after American physician Henry Stanley Plummer eponymously named after ) and "Parry disease" (named after English physician

Caleb Hillier Parry Caleb Hillier Parry (21 October 1755 – 9 March 1822) was an Anglo-Welsh physician credited with the first report of Parry–Romberg syndrome, published in 1815, and one of the earliest descriptions of the exophthalmic goiter, published in 1825 ...

) have been used to refer to toxic multinodular goiter, toxic adenoma, and toxic diffuse goiter (

); the specific entity in each patient/case is not always clear retrospectively, especially in older

literature Literature is any collection of Writing, written work, but it is also used more narrowly for writings specifically considered to be an art form, especially prose fiction, drama, and poetry. In recent centuries, the definition has expanded to ...

. This is logical given that advanced

medical imaging Medical imaging is the technique and process of imaging the interior of a body for clinical analysis and medical intervention, as well as visual representation of the function of some organs or tissues (physiology). Medical imaging seeks to re ...

that can show what is happening at various places within a thyroid gland inside a living person (such as

nuclear medicine Nuclear medicine or nucleology is a medical specialty involving the application of radioactive substances in the diagnosis and treatment of disease. Nuclear imaging, in a sense, is " radiology done inside out" because it records radiation emi ...

imaging of radioiodine

tracer Tracer may refer to: Science * Flow tracer, any fluid property used to track fluid motion * Fluorescent tracer, a substance such as 2-NBDG containing a fluorophore that is used for tracking purposes * Histochemical tracer, a substance used for ...

uptake) was not available until after the 1940s.

References

External links

{{Thyroid disease Thyroid disease