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Thyroid Function tests

Central hypothyroidism

  • The use of thyroid function tests in the diagnosis of hypopituitarism: definition and evaluation of the TSH Index. (clin endo | pubmed | medscape:free full text)
  • body-weight-adjusted treatment 17711927;

Thyroid nodules

  • AACE (Am Assoc of Clin Endocrinologists) 2006: Med Guidelines for Clin Practice for the Diagn and Managem of thyr nodules: pdf
  • BTS/RCP 2007: Guidelines for the management of thyroid cancer (2 ed): pdf

Thyroid dysfunction in pregnancy

  • [+attached]
  • Recommendations
    • Iodine
      • recommended iodine intake 250mcg/d
      • severe iodine deficiency is a major cause for neurological damage worldwide
    • Hypothyroidism
      • both overt and subclin hypothy: adverse effects on course of pregnancy and developmt of fetus
      • hypothy should be corrected before initiation of pregnancy (aim TSH<2.5U/L)
      • replacemt dose should be augmented early during pregnancy (by 4-6/40 by 30-50%)
      • euthyroidism should be maintained throughout pregnancy (aim TSH<2.5U/L 1st trim, <3U/L 2nd/3rd trim)
      • overt maternal hypothy: a/w damage to fetal intellectual developmt (whether subclin hypothy does, uncertain, but should be treated): need to be corrected ASAP, rpt TFT within 30-40d
      • subclin hypothy: tx improves obstetric outcome (but not yet proven to improve fetal neurological developmt): LT4 tx recommended
    • Hyperthyroidism
      • PTU as first line Tx for hyperthy dur pregnancy (methimazole a/w fetal developmtl abnmlties esp 1st trimester, but may be used if pt intolerant to PTU)
      • Dx or PMHx of maternal Graves' carries risk for fetus
      • ATD tx to mother can induce fetal hypothy
      • transplacental passage of TRAb can cause fetal hyperthy
      • ATD tx: target maternal fT4 at non-pregnant ULN usu'ly protects fetus from hypothy
      • close monitoring of T4, TSH, TRAb, and fetal US incl thyroid recommended for guiding therapy
      • fetal hyperthy does not occur when TRAb levels are nml and ATD tx is not administered
      • surgery may be required in some instances (with preop preparation with PTU, propranolol and iodine; ideally during 2nd trim)
    • Hyperemesis
      • a/w icrd thyroid hormone levels and TSH suppression, pts occasionally thyrotoxic
      • thy hormone level elevation and gestational hyperthyroidism: usu self-remitting, mostly not requiring Tx
      • subclin hyperthy (in this setting) does not require tx, and tx is advised against b/o risk of inducing fetal hypothy
    • Thyroid nodules
      • Bx under US guidance, if appropriate surgery during mid-trimester (delay in tx of low-grade tu until after delivery not considered a danger), pregnancy not thought to adversely affect course of thy malignancy
      • TSH suppression for known thy malignancy: maintain during pregnancy with detectable TSH and T4 at upper end of range for nml pregnancy
      • RAI: not during pregnancy or during lactation
    • Autoimmune thyroid disease
      • common in pregnancy
      • presence of TPO Ab or Tg Ab a/w signif icr in miscarriages
      • T4 tx may reverse that risk
    • PPT (postpartum thyroiditis)
      • closely related to Hashimoto's thyroiditis, in 7% of pp women
      • usu'ly transient hypo/hyperthyroidism
      • icrd risk of later permanent hypothy
      • not clearly linked to pp depression
    • Screening
      • prevalence in pregnancy:
        • overt thyroid disease: 1%
        • subclin hypothy: 2-3%
        • pos ABs: 10-15%
          • only 1 study showed dcr in miscarriage and preterm delivery with LT4 tx of euthyroid AB pos women;
          • at risk of developing hypothy dur pregnancy
      • TRAb: to be checked before preg/ by end of 2nd trim in mother with current or previous Graves' txd with thryoidectomy or RAI, or previous neonate with ,


Src: Endotext |


  • Infectious: {acute|chronic}{suppurative|non~}=septic
  • DeQuervain's=Subacute=granulomatous: enlarged, tender thyroid, RAIU near zero, icrd T4 and Tg, hi ESR; likely viral, lasts for weeks/months, often recurs
  • Autoimmune:
    • Hashimoto's=chronic=lymphocytic: usu persists for years
    • also: painless=silent=postpartum: overlapping features of DeQuervain's and Hashimoto's
  • Riedel's thyroiditis=chron sclerosing=invasive fibrous: overgrowth of connective tissue, often extending into neighbouring structures: extremely hard thyroid
  • Misc: Sarcoid; Amyloid; Radiation; Trauma

Amiodarone-induced thyrotoxicosis

  • T1:
    • [~10%?]
    • = iodine-induced
    • hi uptake on ThyScan, hi vascularity on Doppler-US
    • Rx hi dose ATD [PTU: also acts on conversion] > steroids
  • T2:
    • [~90%?]
    • = cell destruction
    • no uptake on ThyScan [although ?uptake blocked], lo vascularity on Doppler-US
    • Rx steroids > ATD

Andreas Jostel,
4 May 2010, 05:51