Lack of substantial effects of raloxifene on thyroxine-binding globulin in postmenopausal women: dependency on thyroid status

Guidelines for the treatment of hypothyroidism: prepared by the american thyroid association task force on thyroid hormone replacement

BACKGROUND

A number of recent advances in our understanding of thyroid physiology may shed light on why some patients feel unwell while taking levothyroxine monotherapy. The purpose of this task force was to review the goals of levothyroxine therapy, the optimal prescription of conventional levothyroxine therapy, the sources of dissatisfaction with levothyroxine therapy, the evidence on treatment alternatives, and the relevant knowledge gaps. We wished to determine whether there are sufficient new data generated by well-designed studies to provide reason to pursue such therapies and change the current standard of care. This document is intended to inform clinical decision-making on thyroid hormone replacement therapy; it is not a replacement for individualized clinical judgment.

METHODS

Task force members identified 24 questions relevant to the treatment of hypothyroidism. The clinical literature relating to each question was then reviewed. Clinical reviews were supplemented, when relevant, with related mechanistic and bench research literature reviews, performed by our team of translational scientists. Ethics reviews were provided, when relevant, by a bioethicist. The responses to questions were formatted, when possible, in the form of a formal clinical recommendation statement. When responses were not suitable for a formal clinical recommendation, a summary response statement without a formal clinical recommendation was developed. For clinical recommendations, the supporting evidence was appraised, and the strength of each clinical recommendation was assessed, using the American College of Physicians system. The final document was organized so that each topic is introduced with a question, followed by a formal clinical recommendation. Stakeholder input was received at a national meeting, with some subsequent refinement of the clinical questions addressed in the document. Consensus was achieved for all recommendations by the task force.

RESULTS

We reviewed the following therapeutic categories: (i) levothyroxine therapy, (ii) non-levothyroxine-based thyroid hormone therapies, and (iii) use of thyroid hormone analogs. The second category included thyroid extracts, synthetic combination therapy, triiodothyronine therapy, and compounded thyroid hormones.

CONCLUSIONS

We concluded that levothyroxine should remain the standard of care for treating hypothyroidism. We found no consistently strong evidence for the superiority of alternative preparations (e.g., levothyroxine-liothyronine combination therapy, or thyroid extract therapy, or others) over monotherapy with levothyroxine, in improving health outcomes. Some examples of future research needs include the development of superior biomarkers of euthyroidism to supplement thyrotropin measurements, mechanistic research on serum triiodothyronine levels (including effects of age and disease status, relationship with tissue concentrations, as well as potential therapeutic targeting), and long-term outcome clinical trials testing combination therapy or thyroid extracts (including subgroup effects). Additional research is also needed to develop thyroid hormone analogs with a favorable benefit to risk profile.

Thyroid hormones affect recovery from depression during antidepressant treatment

AIMS

The aim of the present study was to evaluate whether thyroid hormonal changes during menopause may affect the development and the course of major depressive disorder.

METHODS

Thirty-nine female patients (n = 17 in pre-menopause; n = 22 in post-menopause) with major depressive disorder based on Diagnostic Statistical Manual of Mental Disorders (4th edition) criteria and who were euthyroid and not on hormonal replacement therapy, participated in a prospective, 6-week, open-label naturalistic study. The Hamilton Depression Rating Scale-17 item, the Montgomery-Asberg Depression Rating Scale, the Clinical Global Impression scale and the Cognitive Failure Questionnaire were administered at baseline, week 1, week 3, and week 6. Levels of thyroid stimulating hormone, total thyroxine and total triiodothyronine were collected at baseline visit.

RESULTS

In the whole sample, particularly in pre-menopausal women, levels of thyroid stimulating hormone-potential markers of subclinical hypothyroidism were correlated with those of less severe but more resistant depressive form. Conversely, total thyroxine levels were correlated with a more severe depression, but high levels of this hormone favored the response to antidepressants. Overall, a diagnosis of subclinical hypothyroidism was associated with a poor response to antidepressant treatment. Finally, total triiodothyronine levels were associated with better cognitive functioning, though they did not influence improvement occurring with recovery.

CONCLUSIONS

Our study suggests that thyroid hormones may have an impact on severity and efficacy of antidepressant treatment. However, our result should be considered with caution and merely as a suggestion due to some methodological limitations. Hence further studies are required to better ascertain the role of thyroid hormones in depression after menopause.

Hypothalamic-pituitary axis and peripheral tissue responses to TRH stimulation and liothyronine suppression tests in normal subjects evaluated by current methods

OBJECTIVE

To reevaluate the responses of thyrotropin-releasing hormone (TRH) stimulation test in baseline condition as well as after the administration of graded supraphysiological doses of liothyronine (L-T(3)) in normal subjects.

DESIGN

To assess various parameters related to the hypothalamic-pituitary axis and peripheral tissue responses to L-T(3) in 22 normal individuals (median age: 30.5 years). Subjects were submitted to an intravenous TRH test at baseline condition and also to the oral administration of sequential and graded doses of L-T(3) (50, 100, and 200 microg/day), each given over 3 days, at an outpatient clinic. Blood samples were obtained for thyrotropin (TSH) and prolactin (PRL) at basal and then 15, 30, and 60 minutes after the TRH injection. Effects of L-T(3) administration on cholesterol, creatine kinase, retinol, ferritin, and sex hormone-binding globulin (SHBG) were also measured at basal and after the oral administration of L-T(3).

MAIN OUTCOME

TRH administration resulted in an increase of 4- to 14-fold rise in serum TSH (8.3 +/- 2.5-fold), and in a slight rise in serum PRL concentrations (3.8 +/- 1.5-fold). Administration of graded doses of triiodothyronine (T(3)) resulted in a dose-dependent suppression of TSH and PRL. Basal thyroxine-binding globulin (TBG) and cholesterol levels decreased, and ferritin and SHBG increased after L-T(3) administration, while creatine kinase and retinol did not change throughout the study. There was a positive correlation between basal TSH and TSH peak response to TRH at basal condition and after each sequential L-T(3) doses. On the other hand, TSH peak response to the TRH test did not predict cholesterol, TBG, ferritin, or SHBG values.

CONCLUSION

Using the current methods on hormone and biochemical analysis, we standardized the response of many parameters to TRH stimulation test after sequential and graded T(3) suppression test in normal subjects. Our data suggest that the evaluation of the responses of the hypothalamus-pituitary axis to TRH test as well as the impact of L-T(3) on peripheral tissues were not modified by the current methods.

Increased Thyroid-Stimulating Hormone Levels Associated with Concomitant Administration of Levothyroxine and Raloxifene

A 47-year-old Caucasian woman had a 3.5-year history of primary hypothyroidism treated with levothyroxine. Her levothyroxine dosage of 0.05 mg/day had been stable for the past 15 months. She was then prescribed raloxifene for prevention of osteoporosis secondary to early menopause. During the next 30 months, her levothyroxine dosage had to be gradually increased. The patient had been taking levothyroxine and raloxifene at the same time each day on an empty stomach. During the months of her levothyroxine dosage changes, however, she separated administration of levothyroxine and raloxifene by 12 hours; the patient then became hyperthyroid. Eventually, her levothyroxine needs decreased, and she returned to the same levothyroxine dosage she had taken before separating administration of the two drugs. These findings suggest that raloxifene decreased the absorption of levothyroxine when the two agents were coadministered. Assessment of causality using the Naranjo adverse drug reaction probability scale resulted in a possible association for this adverse event. Another published case report provides findings similar to our patient's experience. The possibility of a malabsorption interaction between levothyroxine and raloxifene is significant, as hypothyroidism is common among postmenopausal women-the same population that is the target of osteoporosis therapy with agents such as raloxifene. The mechanism by which raloxifene decreases levothyroxine absorption is unknown. Further investigation of this potential interaction is warranted. Until then, clinicians should be alert to the potential for an interaction between raloxifene and levothyroxine.

A one-year follow-up on the effects of raloxifene on thyroid function in postmenopausal women

OBJECTIVE

Estrogens increase serum thyroxine-binding globulin (TBG) and total thyroxine (TT4) concentrations. Serum free thyroxine (FT4) concentrations, however, remain normal. Raloxifene (RAL) is a selective estrogen receptor modulator used to treat postmenopausal osteoporosis. Data on the long-term effects of RAL on thyroid physiology are scanty. We evaluated the effects of RAL administration for 1 year on thyroid function in osteopenic, postmenopausal women.

DESIGN

Fifty osteopenic, postmenopausal women were randomly assigned to receive either RAL (60 mg/day, n = 25) or placebo (PL, n = 25) for 1 year, in a double-blind study. Measurements of serum TBG, TT4, FT4, thyroid-stimulating hormone (TSH), thyroid hormone-binding ratio (THBR), FT4 index (FT4-I) and TT4/TBG ratio were carried out at baseline and after 4 and 12 months of therapy.

RESULTS

Baseline values were similar in both treatment groups. Serum TBG concentrations were increased during RAL treatment from baseline values of 29.60 +/- 0.9 microg/mL to 31.45 +/- 1.33 and 32.34 +/- 1.37 microg/mL at 4 months and 1 year, respectively (P < 0.05, baseline v 1-year values) but were unchanged during PL treatment. A small, insignificant increase in TT4 and TSH concentrations occurred in the RAL group and no changes in the PL group. All other values were unchanged during either treatment.

CONCLUSIONS

These results demonstrate that RAL significantly increased serum TBG levels, but the changes were small and not accompanied by changes in FT4-I, FT4, or TSH concentrations, suggesting that long-term RAL treatment is unlikely to clinically affect the thyroid status in euthyroid, postmenopausal women.

Interaction of estrogen therapy and thyroid hormone replacement in postmenopausal women

Based on the use of estrogen therapy/hormone therapy (ET/HT) in postmenopausal women and the prevalence of hypothyroidism in this population, it is estimated that approximately 5% of all postmenopausal women receive treatment with both ET/HT and thyroid hormone replacement. Hormone therapy generally refers to the combined use of estrogens and progestins, the latter administered on a continuous or intermittent basis. HT is indicated for the treatment of postmenopausal women with intact uteri, whereas ET is used in women who have had hysterectomies. Because of its hepatic first-pass effect, oral estrogen therapy, the most commonly used modality of ET/HT, raises the circulating levels of thyroxine-binding globulin (TBG), thereby increasing the bound fraction and decreasing the free (bioactive) fraction of circulating thyroxine (T(4)). As a consequence, oral ET/HT may increase the T(4) dosage requirements of women being treated for primary hypothyroidism as well as alter the pituitary-thyroid axis in euthyroid women. This paper reviews the potential interaction between ET/HT and thyroid hormone replacement based on the prevalence of their concomitant use, mechanistic aspects of the interaction, and recent clinical studies of the effects of oral ET in euthyroid and hypothyroid women. Other agents known to interact with thyroid hormone replacement, including soy supplements, are also reviewed. Because transdermal ET does not affect TBG levels and would not be expected to alter thyroid function, it may be a preferable modality for postmenopausal women who require concomitant treatment with ET/HT and T(4).