This observational survey with prospective and/or retrospective follow-up is designed to study practices for the initial treatment of hypothyroidism in France without modifying subject treatment.

Thyroid disorder can be central, caused by a deficiency in thyroid stimulating hormone (TSH) production; or peripheral, caused by the decrease in the plasma concentration of thyroid hormones, more specifically of free thyroxine (free T4). Peripheral hypothyroidism is caused by the decrease in the production capacities of the thyroid gland.

The treatment of hypothyroidism is based on the restoration and maintenance of biological (judged on the basis of the standardised TSH and T4 values) and clinical euthyroidism.

A number of forms of thyroid hormones are available in the French market (Euthyral®, Cynomel®, L-thyroxine drops®), of which, Levothyrox® is the most frequently prescribed drug in this category.

The treatment of peripheral hypothyroidism, in particular, is well codified and almost consensual. In France, there is no published observational study, based on which one can document the manner in which subjects are treated. This observational study is set up to document these practices.

OBJECTIVES The principal objectives of this survey is to to get information on the use of Levothyrox in France

• Circumstances of diagnosis
• Record realised
• Terms and conditions of treatment by the general practitioner and/or the endocrinologist

The secondary objective is to evaluate the inclusion criteria for levothyroxine treatment.

For each subject the participating doctor will complete a follow up questionnaire form until the first control level of TSH after the diagnosis of hypothyroidism.

Inclusion Criteria:

• Recently diagnosed hypothyroid subject (either during the inclusion period, or within the 6 previous months) for whom, data related to the diagnosis is available if the diagnosis was not carried out initially by the investigating doctor
• Subject, who has given his/her oral consent for participation

Exclusion Criteria:

• Subject included in clinical trial or having participated in a clinical trial during the last 3 months
• Subject presenting a major and objectifiable risk of not being able to follow-up until the next TSH level (moving, problems encountered during another study, pathology affecting the vital prognosis in the short-term)
• All contraindications to Lévothyrox

Independent, hospital and mixed practice endocrinologists and general practitioners enrolled 1000 subjects.