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What You Can Expect

THYROID blood test BASICS

What you can expect when you begin your Defy Medical program.

The first signs of thyroid disorder are typically identified from symptomology and blood screening of Thyroid Stimulating Hormone (TSH) with other thyroid hormone biomarkers, including free thyroxine (T4, free).

Thyroid Stimulating Hormone (TSH), Serum

  • TSH is used as a first line screening tool to assess thyroid disease. Additionally, health care providers check TSH to monitor disease progression and treatment
  • TSH is high in primary hypothyroidism
  • Low TSH occurs in hyperthyroidism
  • Evaluation of therapy in hypothyroid patients receiving various thyroid hormone preparations although free T3 should also be evaluated along with patient’s symptoms
  • Range: 0.450−4.500 μIU/mL (>10 yr old)
  • Methodology: Electrochemiluminescence immunoassay (ECLIA)

T4 (Thyroxine), Total, Serum

  • Used for the diagnosis of hypothyroidism and hyperthyroidism
  • Free T4 is usually preferred instead of measuring total
  • Reference Range: 4.5−12.0 μg/dL
  • Most physicians order serum free T4 instead of serum total T4
  • Free T4 will provide a better evaluation of bioavailable thyroxine since it tests hormone that is not bound by proteins

T4 (Thyroxine), Free, Serum

  • Measurement of circulating thyroxine not bound to proteins (TBP)
  • Reference Interval: 0.82−1.77 ng/dl (>19 yr old)
  • Methodology: Electrochemiluminescence immunoassay (ECLIA)
  • The thyroid gland produces and secretes T4, otherwise known as thyroxine. Proteins bind to T4 and carry it throughout the bloodstream.
  • Once in the tissues, T4 is released from the proteins and is now free to convert into the more active form called T3
  • Many physicians believe that measuring free T4 is a more sensitive test for thyroid hormone production

Reverse T3 (Triiodothyronine), Serum

  • Labcorp Reference Range: 9.2-24 ng/dL
  • Methodology: Liquid chromatography/tandem mass spectrometry (LC/MS-MS)
  • The rT3 level tends to follow the T4 level: low in hypothyroidism and high in hyperthyroidism
  • Increased levels of rT3 have been observed in starvation, anorexia nervosa, severe trauma and hemorrhagic shock, hepatic dysfunction, postoperative states, severe infection, and in burn patients (i.e., "sick euthyroid" syndrome)
  • This appears to be the result of a switchover in deiodination functions with the conversion of T4 to rT3 being favored over the production of T3
  • The Journal of Clinical Endocrinology & Metabolism states that “the T3/rT3 ratio is the most useful marker for tissue hypothyroidism and as a marker of diminished cellular functioning.”

T3 (Triiodothyronine), Total, Serum

  • Methodology: Electrochemiluminescence immunoassay (ECLIA)
  • Second-order testing for hyperthyroidism in patients with low thyroid-stimulating hormone values and normal thyroxine levels
  • Diagnosis of triiodothyronine toxicosis
  • Triiodothyronine (T3) values >200 ng/dL in adults or > age related cutoffs in children are consistent with hyperthyroidism or increased thyroid hormone-binding proteins
  • In hypothyroidism T4 and T3 levels are decreased. T3 levels are frequently low in sick or hospitalized euthyroid patients
  • Total Triiodothyronine (T3) is not considered a reliable marker for hypothyroidism
  • Free T3 is usually preferred instead of total T3 to provide a better evaluation of bioavailable triiodothyronine

T3 (Triiodothyronine), Free, Serum

  • This test measures the amount of T3 not bound by proteins and available to the tissues, or free T3
  • Many doctors believe that evaluating the levels of free T3 is the best indicator of thyroid function
  • Needed to determine level of active thyroid hormone primarily responsible for regulating metabolism to fuel all cellular functions
  • Reference Interval: 2.0−4.4 pg/ml (>19 yr old)
  • Methodology: Electrochemiluminescence immunoassay (ECLIA)

Thyroglobulin Antibody and Thyroglobulin

  • Measures antithyroglobulin antibodies that are commonly present in patients with Hashimoto's thyroiditis
  • Antibodies against the protein thyroglobulin can result in destruction of thyroid cells. This destruction can lead to hypothyroidism
  • Test will identify positive or negative presence of antibodies with reflex to confirm accuracy
  • Usually ordered as part of a comprehensive thyroid panel when thyroid hormone deficiency is present with no conclusive diagnosis
  • Methodology: TgAb: Beckman Coulter immunometric assay; with either of the following methodologies used for reflex confirmation: Tg-IMA: Beckman Coulter immunometric assay; Tg: Liquid chromatography/tandem mass spectrometry (LC/MS-MS)

Thyroid Peroxidase (TPO) Antibodies

  • Differential diagnosis of hypothyroidism and thyroiditis
  • Antibodies against the protein thyroglobulin can result in destruction of thyroid cells. This destruction can lead to hypothyroidism
  • The highest TPO antibody levels are observed in patients suffering from Hashimoto thyroiditis. In this disease, the prevalence of TPO antibodies is about 90% of cases, confirming the autoimmune origin of the disease
  • autoantibodies also frequently occur (60%–80%) in the course of Graves disease
  • Should be used in conjunction with antithyroglobulin test, since autoimmune thyroiditis may demonstrate a response to antigens other than thyroid microsomes
  • Range: 0-34 IU/ML (>19 yr old)
  • Methodology: Electrochemiluminescence immunoassay (ECLIA)

Thyroxine-binding Globulin (TBG), Serum

  • Abnormal levels (high or low) of thyroid hormone-binding proteins (primarily albumin and thyroid-binding globulin) may cause abnormal T3 concentrations in euthyroid patients
  • Range: 13-39 ug/mL (>19 yr old)
  • Methodology: Immunochemiluminometric assay (ICMA)

Initial screening and panel examples:

TSH screening provides a basic initial understanding of a patients thyroid function. Reduction of circulating thyroid hormone (TH) levels due to primary thyroid failure results in increased TSH production, whereas the opposite occurs when circulating THs are in excess. (Compr Physiol. 2016 Jun 13;6(3):1387-428. doi: 10.1002/cphy.c150027. Hypothalamus-Pituitary-Thyroid Axis. Ortiga-Carvalho TM1, Chiamolera MI2, Pazos-Moura CC1, Wondisford FE3.). Lab results will provide TSH ranges that the physician will use to determine if TSH is too high or low, suggesting hypo or hyper thyroid failure. Testing only TSH can be misleading and overlook certain types of thyroid hormone deficiency. Add free T4 and free T3 to provide a better understanding of function during an initial screening. 

  • TSH
  • Free T4
  • Free T3

Additional tests (that can be helpful) :

Integrative physicians often employ thyroid screening tests as part of a more comprehensive panel that includes screening for other hormone types (i.e., sex and pituitary hormones). Sometimes the symptoms of hypothyroid can be similar and/or overlap with other hormone deficiencies including hypogonadism. 

Thyroid Health 

Symptoms of Hypothyroid:

  • dry, coarse skin and hair
  • fatigue
  • forgetfulness
  • frequent, heavy menstrual periods
  • inability to tolerate cold
  • sleep problems
  • anxiety and/or depression

Defy Medical offers an integrative approach, a different therapy methodology

How thyroid interacts with other hormones

Thyroid function and testosterone:

Doctors who prescribe hormone replacement therapies address multiple hormone systems simultaneously rather than focusing on just a single hormone or hormone axis. All hormones appear to have an influence across different axis, playing a role in the production, secretion, and action of other hormone types. Much of the influence takes place at the hypothalamus pituitary level.

Therefore, some doctors prefer a more comprehensive approach to hormone testing and treatment. This is especially necessary in patients with hypopituitary dysfunction affecting the function of multiple hormone systems. Evidence appears to show a relationship between thyroid hormones and testosterone. Studies show that men with hypothyroidism have a subnormal response of luteinizing hormone (LH) after being administered gonadotropin releasing hormone (GnRH). Hypothyroidism also correlates with low concentrations of free testosterone. When thyroid hormone levels are restored, free testosterone returns to an acceptable range. Conversely, hyperthyroidism causes hyperresponsiveness to gonadotropins, elevated testosterone, and elevated estrogen sometimes leading to gynecomastia in men. A further sign of hypothyroidism's effect on low testosterone is the fact that treating men with thyroid medications can improve their testosterone. One study found that giving hypothyroid hypogonadal men thyroxine (T4) almost doubled their free testosterone levels.

A comparison of serum testosterone and free T3 levels between young and middle aged men shows that age effects pituitary output resulting in the decrease of both hormones as men age. 


Male hypogonadism: More than just a low testosterone
Cleveland Clinic Journal of Medicine. 2012 October;79(10):717-725

ABSTRACT: Confronted with a low serum testosterone level, physicians should not jump to the diagnosis of hypogonadism, as confirmation and thorough evaluation are warranted before making the diagnosis or starting therapy. This review discusses how to approach the finding of a low testosterone value, stressing the need to confirm the finding, the underlying pathophysiologic processes, drugs that can be responsible, and the importance of determining whether the cause is primary (testicular) or secondary (hypothalamic-pituitary).

SUMMARY: A 54-year-old man is referred for evaluation of low testosterone. He had seen his primary care physician for complaints of diminished libido and erectile dysfunction for the past year and worsening fatigue over the past few years. He has not been formally diagnosed with any medical condition. On physical examination, he is obese (body mass index 31 kg/m2) with a normal-appearing male body habitus, no gynecomastia, and normal testicles and prostate gland. The patient’s low serum testosterone was confirmed on subsequent measurements at 8 am, with levels of 128 and 182 ng/dL (reference range 249–836). Other laboratory values:

  •  LH 1.4 mIU/mL (reference range 1.2–8.6)
  • FSH 2.7 mIU/mL (1.3–9.9 mIU/mL) (Both of these values are inappropriately normal in the setting of the low testosterone.)
  • TSH 248 μIU/mL (0.4–5.5)
  • Prolactin 24.6 ng/mL (1.6–18.8).

The patient was started on levothyroxine replacement therapy and after 3 months was noted to be euthyroid (TSH 1.8 μIU/mL) and to have a normal serum prolactin level. Testosterone levels (8 am) at this time were 350 ng/dL and 420 ng/dL.

Therefore, the cause of this patient’s hypogonadism was severe hypothyroidism and associated mild hyperprolactinemia. This case shows that a thorough evaluation is warranted before initiating testosterone therapy.


References:

1) Thyroid, 2004, 14 Suppl 1:S17-25, “The interrelationships between thyroid dysfunction and hypogonadism in men and boys” 
2) Horm Res, 1990, 34:215 218, “Reproductive Endocrine Functions in Men with Primary Hypothyroidism: Effect of Thyroxine Replacement” 

3) Clinical Endocrinology, Feb 2000, 52(2):197 201, “Testicular dysfunction in men with primary hypothyroidism; reversal of hypogonadotrophic hypogonadism with replacement thyroxine” 

4) Cleveland Clinic Journal of Medicine, October 2012 vol. 79 10 717-725, “Male hypogonadism: More than just a low testosterone” 

5) The Journal of Clinical Endocrinology & Metabolism, 2008, 93(5):1815-1819, “Erectile Dysfunction in Patients with Hyper- and Hypothyroidism: How Common and Should We Treat?” 

6) Hormone Research, 1990, 34:215-218 7) Eur J Endocrinol. 1995 Jun;132(6):663-7.


Thyroid Hormones and Estrogens:

Patients on thyroid replacement therapy may require larger doses of liothyronine if they are also taking estrogens or estrogen-containing oral contraceptives. The administration of estrogen can increase circulating concentrations of serum thyroxine-binding globulin (TBg). Increased amounts of TBg reduce the clinical response to thyroid agents. Changes in TBg concentration should be taken into consideration when reviewing T4 and T3 laboratory values. Unbound (free) T3 should be measured, rather than total T3 (TT3) (source: Cytomel® (liothyronine) package insert. St. Louis, MO: Jones Pharma Incorporated; 2001 Nov)


Thyroid hormones and Sex Hormone Binding Globulin (SHBG):

Hypothyroidism, or low levels of thyroid hormone, causes a decrease in SHBG. Higher levels of thyroid hormone, as seen with hyperthyroidism and over-dosage of thyroid hormone, causes an increase in SHBG. Fluctuation of SHBG can result in changes in sex hormone bioavailability including testosterone and estradiol. 


Thyroid Hormones and the Growth Hormone Axis:

  • Thyroid hormones work synergistically with growth hormone to influence growth, cellular metabolism and thermogenesis
  • Thyroid hormone (TH) is required for normal growth hormone (GH) synthesis and secretion Leung A.M., Brent G.A. (2016) The Influence of Thyroid Hormone on Growth Hormone Secretion and Action. In: Cohen L. (eds) Growth Hormone Deficiency. Springer, Cham
  • “When the serum concentrations of thyroid hormone increase above the normal range there is an increase in hypothalamic somatostatin tone, which in turn suppresses pituitary GH secretion and overrides any stimulatory effects” Eur J Endocrinol. 1995 Dec;133(6):646-53. Influence of thyroid hormones on the regulation of growth hormone secretion
  • Growth hormone treatment of healthy and GH-deficient subjects is accompanied by increased conversion of thyroxine (T4) to triiodothyronine (T3) in peripheral tissues.
  • Men and women diagnosed with Growth Hormone Deficiency have reduced serum total T3 and increased serum free T4, suggesting a reduction in the function of the deiodinase system J Clin Endocrinol Metab. 2006 Mar;91(3):860-4. Epub 2006 Jan 4. Thyroid morphology and function in adults with untreated isolated growth hormone deficiency

The acute effects of human growth hormone administration on thyroid function in normal men

J Clin Endocrinol Metab. 1988 Nov;67(5):1111-4.

fpo thumbnail article

ABSTRACT: GH replacement therapy may lead to alterations in serum TSH and/or thyroid hormone values in GH-deficient patients, but there is no consensus on the explanation for these changes. We examined the effect of GH administration (0.125 mg, sc, daily for 4 days) on thyroid function in 20 normal men. Serum T4 levels decreased by 8%, and serum free T4 index values decreased by 5%. In contrast, serum T3 levels increased by 21%; serum rT3 did not change. These changes were accompanied by a 54% decrease in the mean serum TSH level. While it is not possible to draw conclusions about hormone production and disposal rates from changes in serum levels, these data are most consistent with enhanced extrathyroidal (including intrapituitary) conversion of T4 to T3 and a compensatory decrease in TSH secretion.

Great resource and explanation of how thyroid hormones are made in the body:

Thyroid Gland, Anatomy and Physiology

fpo thumbnail article v2

Wilmar M. Wiersinga University of Amsterdam, Amsterdam, The Netherlands Available online 17 June 2004

Blood test section sources:

  • Mayo Medical Laboratories (www.mayomedicallaboratories.com)
  • The Journal of Clinical Endocrinology & Metabolism 2005; 90(12):6403–6409; Thyroid Hormone Concentrations, Disease, Physical Function and Mortality in Elderly Men
  • Labcorp.com