Hypothyroidism resident survival guide: Difference between revisions

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*When to take [[Levothyroxine]]: Morning 30-60 minutes before breakfast or 4 hours after last meal of the day. To be taken at the same time each day with water.
*When to take [[Levothyroxine]]: Morning 30-60 minutes before breakfast or 4 hours after last meal of the day. To be taken at the same time each day with water.


*After initiation or change in dose of [[Levothyroxine]] in a patient diagnosed with [[hypothyroidism]], serum [[TSH]] measurements should be done after 4-8 weeks. Once the target TSH level is reached, the TSH level is to be repeated after 6 months, thereafter every 12 months.
*After initiation or change in dose of [[Levothyroxine]] in a patient diagnosed with [[hypothyroidism]], serum [[TSH]] measurements should be done after 4-8 weeks. Once the target [[TSH]] level is reached, the [[TSH]] level is to be repeated after 6 months, thereafter every 12 months.


*In patients who are started on drugs that alter the absorption or metabolism of [[Levothyroxine]], TSH should be measured within 4-8 weeks for dose adjustments.
*In patients who are started on drugs that alter the absorption or metabolism of [[Levothyroxine]], [[TSH]] should be measured within 4-8 weeks for dose adjustments.


*A patient may resume using the previously used full replacement dose of [[Levothyroxine]] after an interruption lasting less than 6 weeks if there was no cardiac event or weight loss in the interim.
*A patient may resume using the previously used full replacement dose of [[Levothyroxine]] after an interruption lasting less than 6 weeks if there was no cardiac event or weight loss in the interim.


*In a patient with [[subclinical hypothyroidism]] with TSH levels between the upper limit of normal and 10mIU/L treatment should be considered if -
*In a patient with subclinical [[hypothyroidism]] with [[TSH]] levels between the upper limit of normal and 10mIU/L treatment should be considered if -
**Patient is symptomatic,  
**Patient is symptomatic,  
**Positive for [[TPOAb]],  
**Positive for [[TPOAb]],  
**Evidence or association with risk factors for [[atherosclerotic cardiovascular disease]], [[heart failure]].
**Evidence or association with risk factors for [[atherosclerotic cardiovascular disease]], [[heart failure]].


*In patients with central hypothyroidism associated with [[adrenal insufficiency]], [[glucocorticoid]] therapy should be given prior to starting Levothyroxine  
*In patients with central [[hypothyroidism]] associated with [[adrenal insufficiency]], [[glucocorticoid]] therapy should be given prior to starting [[Levothyroxine]].


*In patients with central hypothyroidism [[FT4]] levels guide therapy -  target level should be greater than mid-normal range value
*In patients with central [[hypothyroidism]] [[FT4]] levels guide therapy -  target level should be greater than mid-normal range value.


==Don'ts==   
==Don'ts==   

Revision as of 17:49, 26 August 2020

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Ayeesha Kattubadi, M.B.B.S[2]

Overview

Hypothyroidism refers to a clinical state where there is reduced production or action of the thyroid hormone.

Causes


Hypothyroidism can be classified based on the location of the pathology or based on etiology as shown in the table below.[1] [2] [3] [4] [5]

Causes of hypothyroidism
Primary hypothyroidism Central hypothyroidism

( Secondary and Tertiary )

Congenital hypothyroidism
Auto immune Drug induced Iatrogenic Transient

Hypothyroidism

Infiltrative disorders Genetic causes Iatrogenic Tumors Vascular Infiltrative Infectious Miscellaneous
  • Subtotal or Total thyroidectomy
  • Radioiodine therapy
  • External radiation of the neck
  • Iodine deficiency
  • TRH deficiency
  • Isolated CeH
  • Inactive TSH
  • Inactive TRH receptor
  • Transient: overreplacement of T4 in primary hypothyroidism, Sick euthyroid state
  • Trauma: head injury


Diagnosis

Shown below is an algorithm summarizing the diagnosis of [[hypothyroidism]] [6] [7] [8] [9] [10]

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Signs and Symptoms of hypothyroidism are present.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
TSH, free T4 (FT4)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
TSH >5.5mU/L
 
 
 
 
 
 
 
 
TSH 0.5-5mU/L
 
 
 
 
 
 
 
 
 
TSH<0.5mU/L
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
FT4 Low
 
 
FT4 Normal
 
 
 
FT4 Elevated
 
 
FT4 Low
 
 
 
 
 
 
 
 
 
FT4 Low
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
TPOAb
(Thyroid peroxidase antibody)
 
 
Subclinical hypothyroidism
 
 
 
1. T4 to T3 conversion defect
(5' deiodinase deficiency, amiodarone use),
2. Thyroid hormone resistance
 
 
1. Central hypothyroidism,
2. T3 replacement therapy
 
 
 
 
 
 
 
 
 
1. Following excess levothyroxine withdrawal,
2. "Post hyperthyroid" hypothyroidism
( I131 or surgery),
3. T3 replacement therapy,
4.Central hypothyroidism
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Positive
 
Negative
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Central hypothyroidism
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Autoimmune thyroid disease
(Hashimotos disease)
 
1. Euthyroid sick syndrome
2. External radiation
3. Drug induced
4. Iodine deficiency
5. Congenital hypothyroidism
6. Seronegative autoimmune thyroid disease
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Brain MRI
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Abnormal
 
Normal
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Pituitary or Hypothlamus lesion
 
Congenital TRH, TSH deficiency,
Infiltrative diseases
 
 
 
 

Treatment

Shown below is an algorithm summarizing the treatment of Primary hypothyroidism. [11] [12]

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Primary hypothyroidism
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
TSH > 5.5mU/L,
FT4 Low
 
 
 
 
 
 
 
 
TSH = 5.5 - 10 mU/L,
FT4 Normal
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Start Levothyroxine
 
 
 
 
 
 
 
 
Symptoms of hypothyroidism
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Measure TSH after 4-6 weeks
 
 
 
Present
 
 
 
 
 
 
 
Absent
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Goal TSH = 0.4-4mU/L
Adjust levothyroxine dose if goal TSH not reached
 
 
 
Levothyroxine trial for 3-6 months.
 
 
 
 
 
 
 
 
TPoAB
(Thyroid Peroxidase) Antibodies
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Symptoms of hypothyroidism
 
 
 
 
 
 
Positive
 
Negative
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Resolved
 
Unresolved
 
 
 
 
Follow up with annual TSH
 
Follow up with TSH every 3 years
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Lifelong levothyroxine therapy
 
 
 
 
 
 
 
 
 
 

Shown below is an algorithm summarizing the treatment of Central hypothyroidism. [13]


 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Central hypothyroidism
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
TSH<0.5mU/L
0r 0.5-5.5mu/L, FT4 Low
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Adrenal insufficiency
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
No
 
 
 
 
 
 
 
 
 
 
 
Yes
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
MRI Brain
 
 
 
 
 
 
 
 
 
 
 
Give glucocorticoids for 1-2 weeks to prevent adrenal crisis
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Tumor
 
 
 
 
 
 
 
 
 
 
 
Levothyroxine
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Present
 
Absent
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Consider Surgery
 
Levothyroxine
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Reassess by measuring FT4
Goal FT4 is
upper limit of normal
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Do's

[14]

  • When to take Levothyroxine: Morning 30-60 minutes before breakfast or 4 hours after last meal of the day. To be taken at the same time each day with water.
  • After initiation or change in dose of Levothyroxine in a patient diagnosed with hypothyroidism, serum TSH measurements should be done after 4-8 weeks. Once the target TSH level is reached, the TSH level is to be repeated after 6 months, thereafter every 12 months.
  • In patients who are started on drugs that alter the absorption or metabolism of Levothyroxine, TSH should be measured within 4-8 weeks for dose adjustments.
  • A patient may resume using the previously used full replacement dose of Levothyroxine after an interruption lasting less than 6 weeks if there was no cardiac event or weight loss in the interim.
  • In patients with central hypothyroidism FT4 levels guide therapy - target level should be greater than mid-normal range value.

Don'ts

[14]

  • Serum FT3 or Total T3 levels – NOT to be used to diagnose hypothyroidism.
  • In hospitalized patients, TSH measurements should not be done to assess thyroid function unless there is a high index of suspicion for thyroid disease.
  • Cholesterol levels, muscle enzymes, reflex relaxation time - cannot be used as diagnostic tools for hypothyroidism.
  • Do not use thyroid replacement therapy for weight loss in obesity if the patient is euthyroid.
  • Iodine supplementation/ iodine-rich foods should not be used in iodine-sufficient areas for hypothyroidism.
  • Do not use Selenium for preventing or treating hypothyroidism.
  • Do not use desiccated thyroid hormone for the treatment of hypothyroidism.

References

  1. Rizzo LFL, Mana DL, Serra HA (2017). "Drug-induced hypothyroidism". Medicina (B Aires). 77 (5): 394–404. PMID 29044016.
  2. Falhammar H, Juhlin CC, Barner C, Catrina SB, Karefylakis C, Calissendorff J (2018). "Riedel's thyroiditis: clinical presentation, treatment and outcomes". Endocrine. 60 (1): 185–192. doi:10.1007/s12020-018-1526-3. PMC 5845586. PMID 29380231.
  3. Gupta V, Lee M (2011). "Central hypothyroidism". Indian J Endocrinol Metab. 15 (Suppl 2): S99–S106. doi:10.4103/2230-8210.83337. PMC 3169862. PMID 21966662.
  4. Vural Ç, Paksoy N, Gök ND, Yazal K (2015). "Subacute granulomatous (De Quervain's) thyroiditis: Fine-needle aspiration cytology and ultrasonographic characteristics of 21 cases". Cytojournal. 12: 9. doi:10.4103/1742-6413.157479. PMC 4453108. PMID 26085833.
  5. Kumar PG, Anand SS, Sood V, Kotwal N (2005). "Thyroid dyshormonogenesis". Indian Pediatr. 42 (12): 1233–5. PMID 16424561.
  6. Ladenson PW, Singer PA, Ain KB, Bagchi N, Bigos ST, Levy EG; et al. (2000). "American Thyroid Association guidelines for detection of thyroid dysfunction". Arch Intern Med. 160 (11): 1573–5. doi:10.1001/archinte.160.11.1573. PMID 10847249.
  7. Walsh JP, Bremner AP, Feddema P, Leedman PJ, Brown SJ, O'Leary P (2010). "Thyrotropin and thyroid antibodies as predictors of hypothyroidism: a 13-year, longitudinal study of a community-based cohort using current immunoassay techniques". J Clin Endocrinol Metab. 95 (3): 1095–104. doi:10.1210/jc.2009-1977. PMID 20097710   20097710  Check |pmid= value (help).
  8. Fitzgerald SP, Bean NG, Falhammar H, Tuke J (2020). "Clinical Parameters Are More Likely to Be Associated with Thyroid Hormone Levels than with Thyrotropin Levels: A Systematic Review and Meta-analysis". Thyroid. doi:10.1089/thy.2019.0535. PMID 32349628    32349628   Check |pmid= value (help).
  9. Peeters RP (2017). "Subclinical Hypothyroidism". N Engl J Med. 376 (26): 2556–2565. doi:10.1056/NEJMcp1611144. PMID 28657873.
  10. Persani L, Brabant G, Dattani M, Bonomi M, Feldt-Rasmussen U, Fliers E; et al. (2018). "2018 European Thyroid Association (ETA) Guidelines on the Diagnosis and Management of Central Hypothyroidism". Eur Thyroid J. 7 (5): 225–237. doi:10.1159/000491388. PMC 6198777. PMID 30374425.
  11. Okosieme O, Gilbert J, Abraham P, Boelaert K, Dayan C, Gurnell M; et al. (2016). "Management of primary hypothyroidism: statement by the British Thyroid Association Executive Committee". Clin Endocrinol (Oxf). 84 (6): 799–808. doi:10.1111/cen.12824. PMID 26010808.
  12. Chakera AJ, Pearce SH, Vaidya B (2012). "Treatment for primary hypothyroidism: current approaches and future possibilities". Drug Des Devel Ther. 6: 1–11. doi:10.2147/DDDT.S12894. PMC 3267517. PMID 22291465.
  13. Persani L (2012). "Clinical review: Central hypothyroidism: pathogenic, diagnostic, and therapeutic challenges". J Clin Endocrinol Metab. 97 (9): 3068–78. doi:10.1210/jc.2012-1616. PMID 22851492.
  14. 14.0 14.1 Schmoldt A, Benthe HF, Haberland G (1975). "Digitoxin metabolism by rat liver microsomes". Biochem Pharmacol. 24 (17): 1639–41. PMID https://doi.org/10.4158/EP12280.GL Check |pmid= value (help).


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